Beef up overlay_config capability

[bctcvai]

MediaType objects define an overlay_config. The overlay config is then processed to utilize the draw layer once or per-frame based on this configuration.

Currently, the features are limited to time overlay or attribute overlays.

Note: Applets can make use of the same overlay capabilities in real-time, one exists that displays "tally counts" that is updated on frame change.

Work to be done 1.) The schema for this capability is lacking. It should be documented and accessible via swagger 2.) The features should then become more apparent, but additional ones can be added to faciliate new use cases: a.) Watermark capability, measurement aid, etc. - Use-case: Place an SVG at a given position on the canvas. - Considerations: Duration, frame range, etc. Be able to control brush color, etc. b.) Generate a user-identifying QR code and place on a given position on the canvas. - A user-identifying QR code to inject on each video frame. c.) Expose interface to drawGL functions (e.g. drawLine, drawPoly) if SVG interface is insufficient.

3.) There is an option in the UI to turn on/off text overlays, this may be expanded to include each overlay in the config; if it can be set by a user (QR code one may be an example where it is not desired to be disable-able)