Fix some bugs in Financial app

- Try to mark as bold, only imbalance transactions related by
AccountTransaction data: Payable and receivable accounts, uses a different
view of AccountTransaction data(errors ocurred when trying visualize them).

- When create a transaction coming of till entry, use till_entry.identifier as
transaction code(instead till_entry.id): The id was not an understandable value to user.

Change-Id: I9d7525eee7805a96e0dfd8bbb575672bb3eab90c