Tweak behavior of submit buttons on register and login pages

Studio Sass Mixin/Extend Re-Org

Studio: Revises Course Updates Nav Visual Display Issue

The buttons are not re-enabled if the registration/login submission succeeds
(and, therefore, the user is about to be directed to another page). Also, any
error message that is present does not disappear immediately before the page
redirects.

Fix section release acceptance test failure.

Studio internationalization

[STUD-431] Seems like the Edit/QA links in LMS are triggered by a ENABLE_LMS_MIGRAT...

Add management command to Studio for exporting all courses; useful for periodic backups of course content in Studio

[STUD-406] Fix/cdodge/unescape quote strings

change serialize_field to check for type. If value is a string, simply return that, otherwise do a json.dumps

vagrant: Always mount `node_modules` folder after Vagrant NFS mount

Added documentation to new acceptance test features and techniques

Bugfix for stanford shib

Fixed a spelling mistake. LMS-605

Jonahstanley/refactor global to world

Seems like the Edit/QA links in LMS are triggered by a ENABLE_LMS_MIGRATION feature flag. So when running as mongo-backed, set that to False

Tidy up argument parsing in release email script

Add a 'string literal' serialization method and use it in the lambda function mapping table when the value to xml serialize is of basestring type. Also a couple of drive-by pep8 fixes.

Fix alt text for the login page: LMS-600