Added translation for the `agency` dropdown menu.
Renamed ForwardingTransitionController, to support the same lookup for tasks and for forwardings.

Only when the name is identical, the adapter lookup (see https://github.com/4teamwork/opengever.core/blob/65af2a06b2098034e18c1bf911f1a0f620005be7/opengever/task/viewlets/actionmenu.py#L28) works correctly for forwardings too.
Merge pull request #618 from 4teamwork/pg_agency_button

Fixes actionmenu for forwardings.