[FIX]res_user : replace field to show latest connection in tree view
[FIX] base: use correct field for user's last connection.

 We need to display user's last login date, not inherited res.partner ``date``
 field. This has been renamed from 'date' to 'login_date' in revision-id:
   tde@openerp.com-20120810081632-a4sg4ve68gpx6bx4