WIP: Fixing image questions, using invisible fields, and shadow form.
Change timing and sequence of save-like events.
Highlight prediction questions where "submit" hasn't been clicked.
Add "require_image_url" for image questions – used in JS prediction logic

Snapshot questions must have a image_url for the question to be considered answered.

This isn't true for drawing questions.
Rename / move / consolidate / cleanup.
Fix "Replace Snapshot" bug. [#60736740]

https://www.pivotaltracker.com/story/show/60736740