Add edX video ID section

Added the video_course.rst file to describe what course teams do after automated processing is complete.
@nasthagiri, @frrrances, @WatsonEmily , @lou-wang, @srpearce 
@mhoeber, @catong FYI.
Perhaps Steps 11 and 13 should not be steps, but highlighted Notes?  Since they are not additional steps to follow, but rather things to NOT do.