Remove autoplay for video in course about page

The iframe was generated with autoplay=1, which, sometimes, would cause
the video to play in the background.
missed rst
further explanation on entry_points
add infinity symbol to calc preview
Fix URLs for static resources
Correct misaligned django-cas integration
Make forum comment buttons activate by keyboard

Neither edit nor delete activated on pressing the space key.
making LMS modal buttons more flexible to handle longer strings in translation, eg. French
Merge pull request #2805 from edx/gprice/comment-edit-button-key-activation

Make forum comment buttons activate by keyboard
Merge pull request #2806 from edx/frances/fix/lms-modal-button

making LMS modal buttons more flexible to handle longer strings in trans...
Support xblocks with children on the container page.

STUD-1363
Merge pull request #2517 from ionis-education-group/remove-video-autoplay

Remove autoplay for video in course about page
updating commit
Merge pull request #2817 from edx/jarv/update-js-draw-commit

updating commit
Allow HTML in grader messages.
Reformatted event type info to get it out of wide tables
Merge pull request #2800 from edx/ahodges/documentation/reformatevents

Reformatted event type info to get it out of wide tables
xblock-mentoring: Add repository to requirements & installed apps

Adding to installed Django applications is required due to the use
of a Django model by the XBlock
Activate XBlocks by default in LMS & Studio
Merge pull request #2814 from gsehub/xblock-mentoring

xblock-mentoring: Add repository to requirements & installed apps