Problem:
* Region rect was pretty much a hidden editor. Because it was annoying for it to pop up automatically, it did not.
* Because it did not, most users have no idea it even exists.
* But because it is a transient editor, it would steal focus of other editor and annoy users.
Solution:
* Editor has been moved to a window.
* Regions that can be edited add a button below the region which can be pressed to open the editor.
This required a slight change in EditorInspectorPlugin to allow custom editors to be below others.
4044cc7d57