IDI-104: Interim commit: trackList subcomponent being used for captions and transcripts.

Should factor template out into its own file, and see if I can use the same subcomponent for the video sources list.
Still need to add validation.
IDI-104: Move the tracklist into its own file
IDI-104: Refactor JS to eliminate duplication; add UIO files.

Still:
- need to render trackForm title, not hard-code
- need field for video title
- proper validation feedback
etc.