Purpose of this commit is to add some missing fields in message view, notably
is_internal newly added flag and its ratings. Rating form view is also
updated to display is_internal flag, and form view is a bit reorganized.
Task ID 2071556
PR #38692
Somehow having views could be necessary. Previously the only way to see
notifications was embedded inside mail.message views (notification_ids).
Task 2118599
PR #39460
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>