SOL-1, SOL-2, SOL-3

This feature allows upload of video assets to S3. This requires that the
VIDEO_UPLOAD_PIPELINE setting be properly configured and that each
course be configured with a token issued by the media team for their
processing purposes (e.g. linking the video with a YouTube channel).

Co-authored-by: Greg Price <gprice@edx.org>

All forward facing wording changed to Export to Git
Export to git functions removed from management command and put in common file
Additional error checking and documentation improvements
Nitpicks and other minor fixes

This has caused confusion, since this file gets imported when trying to
import the requests library.  And besides, how was this file about
requests in the first place?  Helpers is a much better name.

Our designers find it helpful to be able to stub out simple views that aren't ready
to be seen for production yet, and check them into version control so that other
people can see them and provide feedback. This commit introduces a few new files
and directories for this purpose, as well as a sample view that will only be seen
in dev mode, and never in production.