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.
I respectfully disagree here too - we don't want to say "locate the video component window then click **Edit**." I'd just add a comma after "window."