Remove unnecessary extra line in Panel visual test.
Latest build files.
Rework jqc.Mask a bit to display the spinner image as a background image, and to be able to more easily style it.

Also add a skeleton for some unit tests (although don't have time to implement right now).
Have the Collection View's mask default to showing its spinner.
Add `refs` config to jqc.app.Controller, and allow `addRef()` method to take a "refs" configuration object.