Added UI functionality to allow Three Tab OA Creation
Merge branch 'authoring' of https://github.com/edx/edx-ora2 into grady/authoring_front_end

Included as a seperate commit so that merge can be examined if broken.

Conflicts:
	AUTHORS
	apps/openassessment/xblock/static/js/openassessment.min.js
	apps/openassessment/xblock/studio_mixin.py
	openassessment/xblock/openassessmentblock.py
	openassessment/xblock/xml.py
Finished OA editing in three tabs
Merge pull request #413 from edx/grady/authoring_front_end

Changed studio editing of open assessment blocks to have three tabs and changed validation process to accommodate