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.
Remove Step 6. If they're using the edX ID, then we want them to keep the Video Download Allowed default as is, which is True. After they supply the edX ID, instruct users to click Save.