Non-persisted studio templates

Add boilerplate option to ItemFactory
Minor start date fix to not use microsecs

Reinstate problem_check event as Problem Checked event

The defaults used to be rerandomize=always, showanswer=closed. This is
preserved for capa problems being imported from XML. However, for
courses, and for problems created in Studio, the default has been
changed to never/finished, to match the previous defaults used by
Studio.

Instead, we use XModule field default values when creating an empty
XModule. Driven by this use case, we also allow for XModules to be
created in memory without being persisted to the database at all. This
necessitates a change to the Modulestore api, replacing clone_item with
create_draft and save_xmodule.

This standardizes the XModule field default values to be the same as the
values that are presented by studio when a component is added to a
course.

changed transifex project to edx-platform

Update MathJax to the latest stable version (2.2), to fix IE10 bug LMS-194

Tweak behavior of submit buttons on register and login pages

DraftModuleStore was originally designed as a mixin, but never used that
way, and with the upcoming changes to use the versioned module store,
never will be. This changes removes a circular dependency between
mongo.py and draft.py.

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