Return individual mapped response for Electronic Bank Statements

[Daanvm]

This also requires a new mapper for Electronic Bank Statements. For my current use-case it is good enough to only return the created transaction numbers. I'm not sure how much more effort it is to create a mapper for all fields.

[willemstuursma]

There was a request from @modernmindsnl in #14 to add Electronic Bank Statements.

@Daanvm you could just add them and then @modernmindsnl could expand on your implementation if he / she needs any further fields.