Fixes some of access rights issues. This addons branch features :
- message_is_follower field added in invisible in all views using Chatter
- update of message_follower_ids, to use message_is_follower, and to properly handle users not having access to the res.partner model (ex: basic portal users, anonymous users)
- misc access rights tuning
bzr revid: abo@openerp.com-20120928173655-uh9rzio2zpl8vfpx