zone - agence relation bug

[rougga]

when zone is deleted the agency needs to stay in DB to save data so if the user wants to put is in other zone o new one he can without creating the agency from scratch and restoring its data .
when deleting an agency teh row in table rougga_zone_agence relation table the row need to be deleted but not the zone;
ask the client if an agency can have more than one zone.