Don't set reference_type field on account.move required=True, because it
causes a lot of problems in other modules that don't depend on this one.
Setting it as required in the view is enough.
Improvements include:
- full re-organisation of modules and big re-organisation of the code
- simplification of the code related to the fact that support for direct debit is now in t
he base module, not added by an optional module account_direct_debit (module was removed)
- new design of the wizard to select move lines to pay
- support for non-SEPA file transfer-
- support for German direct debit SEPA files (fixes bug #129)
- remove workflow of payment.order
- add wizard of selection of move lines to pay
