Introduce a constructor parameter for the StateDB called `keep`, which tells
how many checkpoints to keep.  When doing a new checkpoint, if the number of
existing checkpoints exeeds `keep`, the oldest ones will be deleted.

PriceUpdater:
    - Pass context so that it can be canceled during an update loop
    - Define APITypes to make it explicit which API we are using

Previously the Synchronizer required the initial variables of the smart
contracts to be passed as a configuration parameter (that the node took from
the configuration file).  The same applied to the blockNumber.

The last update of the smart contracts introduced events for each smart
contract constructor (initializer), which allows querying the initial variables
as well as the initial block number for each smart contract.

Now the synchronizer uses this information, and thus the initial variables and
the starting block numbers have been removed from the configuration.

- API:
	- Replace `emergencyModeStaringTime` by `emercengyModeStartingBlock`
- Synchronizer:
	- Track emergency mode starting block
- cli/node
	- Add working coordinator config
- coordinator:
	- Retry handler for synchronizer stats in case of error (instead of
	  waiting for the next block to try again)
	- On init, trigger an initial call to the handler for synced block
	  before waiting for the synchronizer, to force the coordinator to start
	  its logic even if there's no new block right after the node has been
	  started (very useful for running in testnet where the frequency of
	  blocks is variable)
	- Merge Msg for synced block and updated vars into one: `MsgSyncBlock`.

- API
	- When updating network info, handle cases where no batches exists and
	  where no forgers exists
- cli/node
	- Update `cfg.buidler.toml` config file to a working version
- common
	- Add new smart contract structs and extend some existing ones to
	  reflect updates regarding events from the smart contracts
- SQL
	- Add new tables and extend existing ones to reflect updates regarding
	  events from the smart contracts
- db/historydb
	- Add functions to insert new smart contract events data
	- Fix unclosed rows that led to inconsistent sql driver state (replace
	  NamedQuery by NamedExec).  This fixes the error:
	  `pq: unexpected Parse response 'C'`
- db/l2db
	- Close rows after usage
- eth
	- In Rollup event, introduce a new UpdateBucketsParameter when there's a
	  SafeMode event, with `SafeMode = true`
- synchronizer
	- synchronize new events
	- avoid calling `auction.CanForge` before the genesisBlock to avoid
	  getting a revert.

- Common:
	- Rename Block.EthBlockNum to Block.Num to avoid unneeded repetition
- API:
	- Add UpdateNetworkInfoBlock to update just block information, to be
	  used when the node is not yet synchronized
- Node:
	- Call API.UpdateMetrics and UpdateRecommendedFee in a loop, with
	  configurable time intervals
- Synchronizer:
	- When mapping events by TxHash, use an array to support the possibility
	  of multiple calls of the same function happening in the same
	  transaction (for example, a smart contract in a single transaction
	  could call withdraw with delay twice, which would generate 2 withdraw
	  events, and 2 deposit events).
	- In Stats, keep entire LastBlock instead of just the blockNum
	- In Stats, add lastL1BatchBlock
	- Test Stats and SCVars
- Coordinator:
	- Enable writing the BatchInfo in every step of the pipeline to disk
	  (with JSON text files) for debugging purposes.
	- Move the Pipeline functionality from the Coordinator to its own struct
	  (Pipeline)
	- Implement shouldL1lL2Batch
	- In TxManager, implement logic to perform several attempts when doing
	  ethereum node RPC calls before considering the error. (Both for calls
	  to forgeBatch and transaction receipt)
	- In TxManager, reorganize the flow and note the specific points in
	  which actions are made when err != nil
- HistoryDB:
	- Implement GetLastL1BatchBlockNum: returns the blockNum of the latest
	  forged l1Batch, to help the coordinator decide when to forge an
	  L1Batch.
- EthereumClient and test.Client:
	- Update EthBlockByNumber to return the last block when the passed
	  number is -1.

- API:
	- Modify the constructor so that hardcoded rollup constants don't need
	  to be passed (introduce a `Config` and use `configAPI` internally)
- Common:
	- Update rollup constants with proper *big.Int when required
	- Add BidCoordinator and Slot structs used by the HistoryDB and
	  Synchronizer.
	- Add helper methods to AuctionConstants
	- AuctionVariables: Add column `DefaultSlotSetBidSlotNum` (in the SQL
	  table: `default_slot_set_bid_slot_num`), which indicates at which
	  slotNum does the `DefaultSlotSetBid` specified starts applying.
- Config:
	- Move coordinator exclusive configuration from the node config to the
	  coordinator config
- Coordinator:
	- Reorganize the code towards having the goroutines started and stopped
	  from the coordinator itself instead of the node.
	- Remove all stop and stopped channels, and use context.Context and
	  sync.WaitGroup instead.
	- Remove BatchInfo setters and assing variables directly
	- In ServerProof and ServerProofPool use context instead stop channel.
	- Use message passing to notify the coordinator about sync updates and
	  reorgs
	- Introduce the Pipeline, which can be started and stopped by the
	  Coordinator
	- Introduce the TxManager, which manages ethereum transactions (the
	  TxManager is also in charge of making the forge call to the rollup
	  smart contract).  The TxManager keeps ethereum transactions and:
	  	1. Waits for the transaction to be accepted
		2. Waits for the transaction to be confirmed for N blocks
	- In forge logic, first prepare a batch and then wait for an available
	  server proof to have all work ready once the proof server is ready.
	- Remove the `isForgeSequence` method which was querying the smart
	  contract, and instead use notifications sent by the Synchronizer to
	  figure out if it's forging time.
	- Update test (which is a minimal test to manually see if the
	  coordinator starts)
- HistoryDB:
	- Add method to get the number of batches in a slot (used to detect when
	  a slot has passed the bid winner forging deadline)
	- Add method to get the best bid and associated coordinator of a slot
	  (used to detect the forgerAddress that can forge the slot)
- General:
	- Rename some instances of `currentBlock` to `lastBlock` to be more
	  clear.
- Node:
	- Connect the API to the node and call the methods to update cached
	  state when the sync advances blocks.
	- Call methods to update Coordinator state when the sync advances blocks
	  and finds reorgs.
- Synchronizer:
	- Add Auction field in the Stats, which contain the current slot with
	  info about highest bidder and other related info required to know who
	  can forge in the current block.
	- Better organization of cached state:
		- On Sync, update the internal cached state
		- On Init or Reorg, load the state from HistoryDB into the
		  internal cached state.

- Allow starting the DebugAPI from the node via config
- In StateDB:
    - Make checkpoints when ProcessTxs() succeeds
    - Remove extra hardcoded `statedb` path that was redundant
    - Replace hardcoded `[:4]` by `[:]` when parsing idx, which failed because
      idx is 6 bytes length now.
- Extra: In node, use waitgroup instead of `stoppedXXX` channels to wait for
syncrhonizer goroutines to finish.

- node:
    - Extend config to add initial variables of the smart contracts used as
      defaults before they are changed via events.
    - In stopped channels, set size 1 so that panics are not witheld until the
      node stops completely.
- common:
    - In Smart Contract variables, comment:
      - `WDelayerVariables.HermezRollupAddress` because it's not needed.
      - `RollupVariables.Buckets` because there are no events for it, and for
        now it's not used.
- historydb:
    - Add functions to get and set smart contract variables.
- db:
    - Add `Rollback` function in `utils.go` to reduce boilerplate in sql
      transaction rollbacks in defers in db functions.
    - Update `rollup_vars` and `auction_vars` (renamed from `consensus_vars`)
      table, and add `wdelayer_vars` table.
- synchronizer:
    - Synchronize WDelayer
    - Handle SC variables properly
- test/ethclient:
    - Add essential implementation of WDelayer

- Move smart contract constants and structs for variables to
  common/{ethrollup.go, ethauction.go, ethwdelayer.go}:
    - This removes repeated code of the structs for variables
    - Allows reusing the constants and variables from all modules without
      import cycles
- Remove unused common/scvars.go
- In common.BlockData, split data from each smart contract into a sepparate
  field (Rollup, Auction, WDelayer).  This affects the structures that til uses
  as output, and HistoryDB in the AddBlockSCData.
- In Synchronizer:
    - Pass starting block of each smart contract as config, instead of
      incorrectly using the genesis block found in the acution constant (which
      has a very different meaning)
    - Use variable structs from common instead of an internal copy
    - Synchronize more stuff (resolve some TODOs)
    - Fix some issues found after initial testing with ganache
- In eth:
    - In auction.go: Add method to get constants
    - Update README to use ganache instead of buidlerevm as local blockchain
      for testing
    - Update env variables and test vectors to pass the tests with the
      deployment in the ganache testnet.
    - Use ethereum keys derived from paths (hdwallet) in testing to avoid
      hardcoding private keys and generate the same keys from a mnemonic used
      in the ganache tesnet.

- Node
	- Updated configuration to initialize the interface to all the smart
	  contracts
- Common
	- Moved BlockData and BatchData types to common so that they can be
	  shared among: historydb, til and synchronizer
	- Remove hash.go (it was never used)
	- Remove slot.go (it was never used)
	- Remove smartcontractparams.go (it was never used, and appropriate
	  structs are defined in `eth/`)
	- Comment state / status method until requirements of this method are
	  properly defined, and move it to Synchronizer
- Synchronizer
	- Simplify `Sync` routine to only sync one block per call, and return
	  useful information.
	- Use BlockData and BatchData from common
	- Check that events belong to the expected block hash
	- In L1Batch, query L1UserTxs from HistoryDB
	- Fill ERC20 token information
	- Test AddTokens with test.Client
- HistryDB
	- Use BlockData and BatchData from common
	- Add `GetAllTokens` method
	- Uncomment and update GetL1UserTxs (with corresponding tests)
- Til
	- Rename all instances of RegisterToken to AddToken (to follow the smart
	  contract implementation naming)
	- Use BlockData and BatchData from common
		- Move testL1CoordinatorTxs and testL2Txs to a separate struct
		  from BatchData in Context
	- Start Context with BatchNum = 1 (which the protocol defines to be the
	  first batchNum)
	- In every Batch, set StateRoot and ExitRoot to a non-nil big.Int
	  (zero).
	- In all L1Txs, if LoadAmount is not used, set it to 0; if Amount is not
	  used, set it to 0; so that no *big.Int is nil.
	- In L1UserTx, don't set BatchNum, because when L1UserTxs are created
	  and obtained by the synchronizer, the BatchNum is not known yet (it's
	  a synchronizer job to set it)
	- In L1UserTxs, set `UserOrigin` and set `ToForgeL1TxsNum`.

* WIP rebase

* Combine both SQL DBs

* API and DB refactor

The coordinator implementation has been refactored to allow all the goroutines
to be handled from the node.