Completly rework Task Transitioncontroller guards:

 - introduce Conditions helper class
 - Define complete and sensefull tests (dropping Mocktest's)
Actionmenuviewlet: display agency actions, in a separate dropdown button.
Rework inboxtransitioncontroller.

Conflicts:
	opengever/inbox/tests/test_transitioncontroller.py
Pep8 cleanup.
Dropped no longer used transitioncontroller helper methods.
Reworked forwarding test.