Added permission check system, closes #202, #203.  - can be activated by setting ticket_permission_system:    * ticket_permission_system: trac    * ticket_permission_system: update_restricted_to_participants
Added permission check system, closes #202, #203.
 - can be activated by setting ticket_permission_system:
   * ticket_permission_system: trac
   * ticket_permission_system: update_restricted_to_participants

If it is set to trac it will honour the settings that are set in the trac system.

If 'update_restricted_to_participants' is choosen then a ticket update is allowed only if: 
  1) the updater is the reporter, 
  2) the updater is in the CC 
  3) the updater has trac permission to update the ticket. 

If the update is denied, a new ticket will be generated instead as to not loose the issue .



git-svn-id: e959ebe540f258281fb77864025b49ae95417172@398 51ba4ec3-dd23-0410-a888-bc9a71dd14c1

dscho/email2trac,dscho/email2trac,dscho/email2trac,dscho/email2trac