Regions normalize ui

The regions object currently does not support @ui.syntax selectors. In the interest of keeping things DRY this would be useful especially for occasions when a regions DOM element needs to be animated or manipulated somehow in it's LayoutView.

For example:

```
var layoutView = Backbone.Marionette.LayoutView.extend({
    regions: {
        foo: '@ui.bar'
    },
    ui: {
        bar: '.baz'
    }
});
```

I've added a possible solution including unit tests using an updated version of the normalizeUIKeys function.