Move review request draft banner logic into new classes.
This moves all the logic for dealing with draft banners into a set of

new classes in ReviewRequestEditorView. These will allow

ReviewRequestEditorView to dynamically create these banners, instead of

requiring a page reload.
Right now, a page reload is still used, so as not to make this change

any larger than it already is. Dynamic updating will come in a future

change.

Tested each banner state (draft of new review request, draft of published

review request, submitted, discarded), both from the banner generated

when the page was created, and the banner dynamically generated (for the

draft banners only, since the close ones aren't wired up to be dynamic yet).
All button actions worked, as well as editing of text, and display of banner

content.
Unit tests pass.