New Publishing controls on Unit page.

STUD-1707
cleanup of unit, container, and xblock sass; added modules and layout sass; publishing states and actions on new unit
Discard changes in-progress work, to be completed in STUD-1860.
Clear publish flag after sending publish operation, pluse code review cleanup.
Minimal bok choy test for Publish and View Live.
Merge pull request #4246 from edx/christina/unit-publishing2

New Publishing controls on Unit page.