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

cli/node/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/hex"
 	"fmt"
 	"os"
 	"os/signal"
@@ -13,6 +14,7 @@ import (
 	"github.com/hermeznetwork/hermez-node/log"
 	"github.com/hermeznetwork/hermez-node/node"
 	"github.com/hermeznetwork/tracerr"
+	"github.com/iden3/go-iden3-crypto/babyjub"
 	"github.com/urfave/cli/v2"
 )
 
@@ -25,6 +27,15 @@ const (
 	modeCoord = "coord"
 )
 
+func cmdGenBJJ(c *cli.Context) error {
+	sk := babyjub.NewRandPrivKey()
+	skBuf := [32]byte(sk)
+	pk := sk.Public()
+	fmt.Printf("BJJ = \"0x%s\"\n", pk.String())
+	fmt.Printf("BJJPrivateKey = \"0x%s\"\n", hex.EncodeToString(skBuf[:]))
+	return nil
+}
+
 func cmdImportKey(c *cli.Context) error {
 	_cfg, err := parseCli(c)
 	if err != nil {
@@ -196,6 +207,12 @@ func main() {
 					Required: true,
 				}},
 		},
+		{
+			Name:    "genbjj",
+			Aliases: []string{},
+			Usage:   "Generate a new BabyJubJub key",
+			Action:  cmdGenBJJ,
+		},
 		{
 			Name:    "wipesql",
 			Aliases: []string{},