Add a sequence on customers' code

This module adds the possibility to define a sequence for the partner code. This code is then set as default when you create a new commercial partner, using the defined sequence.

The reference field is treated as a commercial field, i.e. it is managed from the commercial partner and then propagated to the partner's contacts. The field is visible on the contacts, but it can only be modified from the commercial partner.

No codes are assigned for contacts such as shipping and invoice addresses. This module is a migration of the original base_partner_sequence addon to OpenERP version 7.0.