erp5_accounting: Allow Assignor manage Accounting Periods

   Fix inconsistency on guard and permissions

   Fixup the inconsistent restart/restart_action transition, that has
     Assignee/Assignor guard in am inconsistent matter.

   Allow assignor have the same permissions and guard than the assignee

   Fix up permissions on delivered state, where the Assignor had no
   permission to view/access accounting period (so deliver by assignor
   only was impossible).