Update BankTranserProcess and BankAccountRevealPasswordProcess to use custom fields on Process

[renatomassaro]

On #386 new bank-related fields were added to the Process struct:

• src_atm_id, src_acc_number
• tgt_atm_id, tgt_acc_number

These fields should be used by BankTransferProcess and BankAccountRevealPasswordProcess. Using them instead of data allows the Process to support signals and add reactions based on events that affect the source or the target bank accounts.