[IMP] res_users,res_partner: login = email
[IMP] res_user: users are create with company_id = actual company_id
[IMP] res_user: on change login, change email
[IMP] res_user: on change login change email for simplified mode
[MERGE] from trunk
[IMP] res_partner: remove has_user_ids
[IMP] res_partner: remove write change
[IMP] res_user: remove overwrite of create who change company_id value
[IMP] res_partner, res_users: small change in views
[MERGE] from trunk
[MERGE] Sync with trunk
[MERGE] Sync with trunk
[IMP] res_users: when specifying an email value, always check it is valid.
[IMP] res_users: improved form view according to task specifications (button -> link, partner_id visible, active moved outside access rights).
[MERGE] Sync with trunk
[REV] users: contraints on login = email style not applicable anymore.
[IMP] res_users: simplified form view: added placeholders, especially for login that should be an email.
[IMP] ir_mail_server: cleaned a message by adding some uppercases.
[MERGE] Sync with trunk
[MERGE] [IMP] User creation flow

Server-side branch:
- res.users simplified form view: login field is called 'Email Address' to try to have email-style login (byt no constraint on the login currently; email and login are still different fields);
- res.users form view: removed contact fields from the user view, but added a link to the partner. It allows to go from the user to the related partner and have access to all its profile data;
- res.partner: email is necessary if user_ids is not empty (aka, partner is an user)