Message are now fetched and display using javascript
to optimize performance.
Also the chatter is completely rewrite : add pager,
filter possiblity, ...
This commit is mainly technical: posting feature does
not change. Only the display with pager is new.
The goal is also to prepare frontend chatter for a
better integration with rating widget.
The mail.thread mixin is extended to manage the field
website_message_ids (display all messages that can be
seen on frontend by user (employee or not).
When fetching or posting message, a check is done to see
if we need to do it as sudo(). website_mail implement posting
messages with token or sha_in (using in website_quote).
The same verification is now done when fetching messages, via
'_special_access_object' method.