V2.2 regions normalize ui

New branch for issue #1649

Adds support for @ui.syntax selectors in regions hash.

For example:

```
var layoutView = Backbone.Marionette.LayoutView.extend({
    regions: {
        foo: '@ui.bar'
    },
    ui: {
        bar: '.baz'
    }
});
```
For your first response: we want to test that using this syntax does ultimately yield a correct region, though.

Second response:
I've gotten the circular ref error before too in other region refactors.  What were you comparing to?
`new Marionette.Region({ el: '.craft' })`?

I just noticed your tests were inside an existing test too.  Can you pull yours out into a separate `describe` dealing with `@ui.`?