[WIP] point_of_sale: refactor error popups in preparation of a multicompany-screwup prevention error popup
[WIP] point_of_sale: checking for consistency between the user and the session's company
[FIX] point_of_sale: the self_checkout related fields are obsolete and should be removed, but we are too late in the release schedule to do so. Marking them as FIXME, to be removed for next major version
[FIX] point_of_sale: prevent inexact payements when there is no cash payment method available as it will crash the backend
[FIX] point_of_sale: activate on screen keyboard for user search
[FIX] point_of_sale: flush orders before closing the pos. This will help prevent users from closing the session with unflushed orders
[FIX] web: failing onchanges should not prevent to save

This patch is related to 82adba4714d9b809aad835d0d77e6b6f9fde8ddc

With the above patch, it wasn't possible anymore to save if an onchange failed. This isn't the expected behavior.
Besides, $.when.apply($, defs) is rejected as soon as one def fails, without waiting other defs to be either resolved or rejected.

This new patch allows to save if onchange fails, and wait for onchanges sequentially.
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-win32