[IMP] Improve Calendar synchronization

    - Use the new fields from calendar (renamed in 9398.1.7 trunk-cal-v8-jke)
    - Manage some google excpetions about token expiration
    - Manage some google excpetions about token revokation
    - Manage some google excpetions about 410 - Gone from google
    - Detect / Allow user to change the calendar and remove all old reference.
    - Use by default the since_modified for synchronization and not always a full (updatedTime in google)
    - Add some key for ir_parameters : 
             'calendar.week_synchro' : number of week to synchornize when we are in full mode
             'calendar.block_synchro_attendee' : need to synchronize the attendees between google and openerp (creation of partner)
             'calendar.block_since_synchro' : Always use the full synchro. (Can be forced in "one time" removing the last synchro from res_users form)
             'calendar.debug_print' : _logger is more verbose
    - Pep 8
    - Change behaviour of do_request to return a tuple with status raquest and response
    - Add field from token and synchro date in res_users view form