Split up Studio view into subviews for each tab.
Implement assessment editing views
A first pass at containers.

Restructred the container to be heavily reliant on DOM structure,
largely ignoring all unique identifiers and shrinking the implicit size
of the Container Item classes

Completed the initial pass of the Container Item Class.

Added tests and fixed major and minor issues.

Conflicts:
	openassessment/xblock/static/js/openassessment.min.js
Integrate container and container item into the rubric editing view.
Minify CSS.
Merge remote-tracking branch 'origin/authoring' into will/js-refactor-assessment-editing

Conflicts:
	openassessment/xblock/static/css/openassessment.css
	openassessment/xblock/static/js/openassessment.min.js
	openassessment/xblock/static/js/src/oa_edit.js
Merge pull request #485 from edx/will/js-refactor-assessment-editing

JS editor refactor