[FIX] Do not lose session.db on authentication error
[IMP] point_of_sale: add constraint on company

Using a payment method belonging to another company will raise errors when closing the session.
To avoid being stuck at session closing, forbid to create a POS using a journal of another company.
[FIX] mrp: traceability of production

When consuming product, the main_production_move is set as the source of production (used for consumed_for parameter)
However the method action_consume now (since 661a204) returns the new moves (when spliting) instead of the original one. This means that the tracebility would fail.
[FIX] project: Overpassed Deadline computation

The field delay_endings_days represents the number of days since the deadline.
This field was using the write_date instead of now to compute it and was using the absolute value (so project in advance would also get overdue days
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-win32