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
@cahrens   agree with note above.  my comments were just for section/subsection levels.  If I understand correctly, clearing hide option for section/subsection will not clear or publish for a unit that is hidden explicitly.

Question though:  clearing hide option from a subsection that contains units with unpublished changes  publishes those changes?  Please confirm.  @dan-f