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
@dan-f   looking at this in sandbox -- in dialog, %(xblockType)s resolves as "unit" for both section and subsection

This is for a section:

![image](https://cloud.githubusercontent.com/assets/5607222/3894403/e58851ea-2243-11e4-89e1-bba3ea586986.png)