Update node and apply some fixes

- 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

config/config.go

@@ -9,6 +9,7 @@ import (
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/hermeznetwork/tracerr"
+	"github.com/iden3/go-iden3-crypto/babyjub"
 	"gopkg.in/go-playground/validator.v9"
 )
 
@@ -37,6 +38,13 @@ type ServerProof struct {
 type Coordinator struct {
 	// ForgerAddress is the address under which this coordinator is forging
 	ForgerAddress ethCommon.Address `validate:"required"`
+	// FeeAccount is the Hermez account that the coordinator uses to receive fees
+	FeeAccount struct {
+		// Address is the ethereum address of the account to receive fees
+		Address ethCommon.Address `validate:"required"`
+		// BJJ is the baby jub jub public key of the account to receive fees
+		BJJ babyjub.PublicKeyComp `validate:"required"`
+	} `validate:"required"`
 	// ConfirmBlocks is the number of confirmation blocks to wait for sent
 	// ethereum transactions before forgetting about them
 	ConfirmBlocks int64 `validate:"required"`
@@ -162,7 +170,8 @@ type Node struct {
 		SyncLoopInterval Duration `validate:"required"`
 		// StatsRefreshPeriod is the interval between updates of the
 		// synchronizer state Eth parameters (`Eth.LastBlock` and
-		// `Eth.LastBatch`)
+		// `Eth.LastBatch`).  This value only affects the reported % of
+		// synchronization of blocks and batches, nothing else.
 		StatsRefreshPeriod Duration `validate:"required"`
 	} `validate:"required"`
 	SmartContracts struct {