Extend statedb and use prefixes, add debugapi

Add L1UserTxs queues system to Transakcio

In statedb:
- Store all values using prefixes for keys to allow iteration
- Add methods MTGetRoot, GetAccounts

Implement debugapi, an http server with debugging endpoints:
- debugAPI.GET("sdb/batchnum", a.handleCurrentBatch)
- debugAPI.GET("sdb/mtroot", a.handleMTRoot)
- debugAPI.GET("sdb/accounts", a.handleAccounts)
- debugAPI.GET("sdb/accounts/:Idx", a.handleAccount)

Add get tokens endpoint

More realistic example amounts

Add transakcio Token Register instructions parser

Add get token endpoint

Fix/rqcompresseddata

Add transakcio coordinator tx instruction feature

Transakcio:
- Transaction generation to fail when Transfer to an account that don't exist (not created yet)
- Add CreateAccountDepositCoordinator instruction feature
- Updated lang.go instruction type parser approach for more simplicity of code
- Remove `*testing.T` from transactions generation methods, use `log.Fatal` instead

Update ethclient rollup iteration 3

Add TxSel Nonce sort. Fix surplus from refactors

- Add TxSel Nonce sort
- Fix surplus from refactors
- StateDB reuse computation of ToIdx across Synchronizer, TxSelector,
BatchBuilder

Impl exit edpoint and refactor pagination

Feature/transakcio

Add transakcio set type definition, add set loading, move transakcio to
package, adapt branch to last master updates (fix compile due new common
types & git conflicts).
Update tests to pass the test, pending to adapt to new Transakcio
interface.

Fix PR #187

(#187 PR was done before another PR (#186) was merged into master, and
when 187 was merged to master, was not compiling due changes from #186
not applied yet to #187)

Update ethclient rollup iteration 2

Change pointers to nil in common (remove common.Struct.parameters pointers for Idx & EthAddr.  Update common parameters)

Feature/integration2

- Implement SlicePtrsToSlice and use it in all `meddler.QueryAll` sql db functions to always return []Foo instead of []*Foo

- Implement new TxID spec that distinguishes L1UserTx and L1CoordinatorTx
- Replace some type []*Foo by []Foo
- Fix HistoryDB & L2DB bug: in case of error, a rollback was applied and the returned error was nil
- Reorder inserts in historydb.NewHistoryDB() to follow foreign key dependencies
- Add initial synchronizer test with test.Client (for now, only tested l1UserTxs, blocks, addToken)
- Update L1UserTx event in test.Client

Update ethclient contracts & rollup iteration 1

Add methods to get ERC20 constants