[FIX] point_of_sale: the order reference used the session sequence number wich was not unique accross sessions on different point_of_sales.

Now we are using the session id which is unique, but is less understandable
[FIX] website_forum: fixed setting an answer as valid / invalid. The change
in the behavior of browse records due to the new API introduced a wrong
behavior, now fixed.
[FIX] website_forum: issue in biography (unnecessary tags added by editor) + menu control (Users / My Profile)
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64