[ADD] account, l10n_*: create transfer account based on prefix.

This commit changes the mechanism to get the transfer account.
As the bank/cash accounts, the transfer account is now created automatically based on
a prefix.

-task: https://www.odoo.com/web#id=35857&action=333&active_id=967&model=project.task&view_type=form&menu_id=4720