Mobile events, updates to video events

@stroilova , @mulby , @nasthagiri , @gwprice , @lou-wang , @mhoeber here is a framework that we can work from to get initial documentation out with the release. Notes:
- I am not sure that the same additional context fields that I see for the v.0 play_video (Olga shared with me) event also apply to all of the other video events.
- the event field names for the new edx.app.browser.launched event in Olga's spreadsheet are very rough
So does this mean we do not at all capture the video's edX ID in mobile-generated video events?
Is there another easily-queryable mapping between module_ids and edx IDs?  The reason I ask is because I envision the edX ID to be a longer-term identifier than the module_id.  The edX ID uniquely identifies a canonical video.  While the module_id identifies a single usage of that video.  If the course author uses the same edX ID across multiple courses and even multiple units within a course (think A/B testing), the analytics data would not capture that.