Enforce type of the XBlocks Fields when set

Update testing.md

Use UrlResetMixin to test GroupConfiguration feature

Make import/export work with split mongo, replace create_xmodule with create_xblock

Bok-Choy CMS Video Tests

Improvements to the release.py script

Redirect to show_reqs for prof ed

- Changes registraiton button text for professional ed courses
- Professional ed courses do not see "choose your track" page; go straight to verification flow

Update xblock-mentoring.

Show Certificates Before End

Add make_course_key to modulestores, so that external clients don't need to assume a CourseKey subtype.

Conflicts:
	common/lib/xmodule/xmodule/modulestore/xml_importer.py

Remove post-publish step.

Refactor all callers (often replacing with more appropriate fn)

Also, added for_branch_setting method to old mongo and removed some
branch verification tests

Conflicts:
	common/lib/xmodule/xmodule/modulestore/mongo/draft.py
	common/lib/xmodule/xmodule/modulestore/split_mongo/split_draft.py
	common/lib/xmodule/xmodule/modulestore/xml_importer.py

Mark it as deprecated, but maintain backwards compatibility.

ECOM-11

Split/add and fixes

Catch InvalidKeyError in course_id_from_url().

This updates the XBlock dependency to edX/XBlock@***
and add the newly introduced enforce_type methods