Support maxNumBatch and atomic transactions

[krlosMata]

New features

maxNumBatch

Allow the user to sign a maxNumBatch parameter when sending a L2 transaction.

• Proposals implementation:
  • Add new param to transaction maxNumBatch which would be chosen by the user
  • Add numBatchOffset and internally compute the maxNumBatch

Atomic transactions

All the rq should be added to allow the user to link transactions.

• Proposals implementation:
  • when a L2 transaction is done, return the necessary data which could be shared afterwards to link transactions. Therefore allow a single object as a parameter to link transactions
  • Add single parameters just related to atomic transactions and sign them internally

[krlosMata]

maxNumBatch feature implemented in #159

[krlosMata]

We would go for the following implementations:

maxNumBatch

Add new param to transaction maxNumBatch which would be chosen by the user

Atomic transactions

Add single parameter (linkedTransaction) just related to atomic transaction and sign them internally.
We will review user/develop flow afterwards and select the best way to incorporate atomic transaction data in higher layer in the library