Add ability to set staff lock from course outline

STUD-1851. @cahrens please review.

Sandbox available at http://studio.benmcmorran.m.sandbox.edx.org/course/edX/Open_DemoX/edx_demo_course
Test also with self._update_staff_locks(False, True, False)?

And what about testing if the source is the vertical itself?
self._update_staff_locks(False, False, True)