getForm implemented.
PostDrops: Added index to error fields name

E.g. A and error field "[56].title" means the drop at position 56 in
the provided list, has a problem with the title.
createForm: Allow creation of fields  simultaneously

* Added a fields property to CreateFormFieldsDTO.
* JpaFormDao#create overriden to persist each form field.
GetAccountDTO: Replace Bucket and River inner classes

Replaced the inner classes with the corresponding GetxxxDTO.
getAccount: Added forms array to GetAccountDTO

* Treated like any other asset.