Document viewer and editor

[BigBlueHat]

Here's an auto-generated one to iterate on:
https://gist.github.com/BigBlueHat/efff3e3c082ee900e503

I did it as a Gist to encourage forking and contribution. 😸

[tilgovi]

The viewer and editor need to be documented in doc/api/ui and those files added to doc/api/ui.rst. There is no fixed schema anymore, just fields expected by the ui modules.