make embargo template theme-able

Use "Stanford-style" theming to enable you to put your own embargo
notice up.
missing themed embargo page fails safely to unthemed
Add SHOW_PROGRESS_SUCCESS_BUTTON feature

Show a button at the top of lms/templates/courseware/progress.html if the
lowest nonzero grade cutoff has been reached. Introduce two settings:
PROGRESS_SUCCESS_BUTTON_URL is the href of that button (the course id is
appended); PROGRESS_SUCCESS_BUTTON_TEXT is the text, defaults to
"Download your certificate"
Make the SHOW_PROGRESS_SUCCESS_BUTTON feature more flexible

The button text default is now in the template and i18n-able, a
PROGRESS_SUCCESS_BUTTON_TEXT_OVERRIDE option is offered in settings.
The button url now uses string formatting.
Add test in import code to make sure two overlapping courses aren't imported
Refactored terminology and added loop break for optimization
04/09/2014 Release Notes

DOC-249
Update Running Acceptance Tests Bok_Choy
Update testing documentation
Fix duplicate save and cancel buttons in Studio

STUD-1531

Also add support for refreshing the modal on custom save
Updated ORA2 to release-2014-04-15
Merge pull request #3339 from edx/andya/fix-duplicate-buttons

Fix duplicate save and cancel buttons showing when editing xblocks
Fix duplicate save and cancel buttons in Studio

STUD-1531

Also add support for refreshing the modal on custom save
Merge pull request #3361 from edx/andya/rc-fix-duplicate-buttons

Fix duplicate save and cancel buttons in Studio
Merge pull request #3359 from edx/will/ora2-release-2014-04-15

Updated ORA2 to release-2014-04-15
Fix batch enrollment box email sending
Documentation for HTML editor upgrade

STUD-1428
Merge pull request #3022 from edx/markhoeber/documentation/STUD-1428

First Draft - Documentation for HTML Editor Changes
Merge pull request #3362 from edx/sarina/fix_batch_enrollment_emails

Fix batch enrollment box email sending
Release notes 4-15-14