Android-specific enhancements for RxUI 6

Opening a PR to track this branch.

## Done:

- [x] Added support for binding to layouts in a list adapter
- [x] Added support for auto-wiring up controls to properties on a view or activity

## TODO:

- [x] Auto-wire-up fragments
- [x] Add more Android samples showing the wire up and list view binding
- [ ] Verify default properties for binding to views. Currently needs to be `myView.TheTextView.Text` instead of `myView.TheTextView`
  ---Not sure on this one.Bind() needs to be on an IViewFor, so a path to the desired control is passed in. With the existing logic, the defaulting never gets called for a non-null control path.

## Notes:
For view binding in a list adapter, the layout should be defined as a
```
<merge xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
.... <!-- your normal layout goes here -->

</merge>
```
To auto wire-up properties to your View/Activity/Fragment subclasses, you'll need to call `this.WireUpControls();` after the layout it set. For Activities, that's usually in OnCreate; in the `ReactiveLinearLayout` it's in the ctor and in Fragments it's in `OnViewCreate`