Also, in the cli commands `wipesql` and `discard`, always rebuild the current
checkpoint of the stateDBs to make sure it's in a consistent non-corrupted
state and do a reset afterwards.  These commands will allow reverting the
StateDB to a valid and consistent state in case a crash leaves the StateDB in a
corrupted state.

- Add config parameter `Coordinator.L2DB.MinPriceUSD` which allows rejecting
  txs to the pool that have a fee lower than the minimum.
- In pool tx insertion, checking the number of pending txs atomically with the
  insertion to avoid data races leading to more than MaxTxs pending txs in the
  pool.

The command is useful in case the synchronizer reaches an invalid state and you
want to roll back a few blocks and try again (maybe with some fixes in the
code).

- cli / node
    - Update handler of SIGINT so that after 3 SIGINTs, the process terminates
      unconditionally
- coordinator
    - Store stats without pointer
    - In all functions that send a variable via channel, check for context done
      to avoid deadlock (due to no process reading from the channel, which has
      no queue) when the node is stopped.
    - Abstract `canForge` so that it can be used outside of the `Coordinator`
    - In `canForge` check the blockNumber in current and next slot.
    - Update tests due to smart contract changes in slot handling, and minimum
      bid defaults
    - TxManager
        - Add consts, vars and stats to allow evaluating `canForge`
        - Add `canForge` method (not used yet)
        - Store batch and nonces status (last success and last pending)
        - Track nonces internally instead of relying on the ethereum node (this
          is required to work with ganache when there are pending txs)
        - Handle the (common) case of the receipt not being found after the tx
          is sent.
        - Don't start the main loop until we get an initial messae fo the stats
          and vars (so that in the loop the stats and vars are set to
          synchronizer values)
- eth / ethereum client
    - Add necessary methods to create the auth object for transactions manually
      so that we can set the nonce, gas price, gas limit, etc manually
    - Update `RollupForgeBatch` to take an auth object as input (so that the
      coordinator can set parameters manually)
- synchronizer
    - In stats, add `NextSlot`

- Node
	- Load Coordinator Fee Account from config
		- Sign the AccountCreationMsg to generate the
		  AccountCreationAuth
		- Resolve #465
	- Wait for synchronizer termination before stopping coordinator to avoid
	  getting stuck when closing in the following case:
		- The coordinator stops reading the synchronizer msg channel,
		  and the node gets stuck sending a message to that channel.
- Common
	- Move account creation auth signature code to common.
	- Update RollupConstInputSHAConstantBytes
- Coordinator
	- Set batch status in the debug file
	- Propagate SCVariables on reorg
	- Pipeline: Get SCVariables updates
		- Resolve #457
	- Fix off by 1 error in Pipeline.shouldL1L2Batch() (which shouldn't have
	  caused any problem, but it was not right)
- KVDB
	- Delete future checkpoints after reset
	- In `ResetFromSynchronizer`, remove all checkpoints first, and follow
	  the same logic as `reset()`.
- Cli
	- Add command to generate a BabyJubJub key pair (to be used for the
	  Coordinator Fee Account)
- Node
	- Adjust example config `Coordinator.L1BatchTimeoutPerc` to avoid
	  missing the L1Batch deadline with the following setup:
		- a block is mined every 2 seconds
		- single proof server that takes 2 seconds to calculate a proof
- TxProcessor
	- Close temporary pebble used for the exit tree after usage.
		- Resolve #463

- Refactor the migrations code so that packr is only called (via an init
  function in `db/utils.go`).
- When loading the migrations, make sure there is at least one migration,
  otherwise panic (this would happen if the node is built incorrectly)

Load an ethereum keystore when the node is started in coordinator mode.  The
private key corresponding to the forger address must be imported into the
keystore before running the node in coordinator mode.  You can see an examples
in `cli/node/load-sk-example.sh`.

- 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

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