Create Suspension Hosts for iOS and Android

This PR adds AutoSuspend support, similar to the WP8 and WinRT support

## iOS Todo

- [x] Create a `SuspensionHost` for iOS
- [x] Add a simple `ISuspensionDriver`, similar to the WP8 and WinRT ones to get people started

## Android Todo

- [x] Create a `SuspensionHost` for Android
- [x] Create the equivalent of RoutedViewHost for Android
- [x] Rig the Back Button on Android
- [x] Add a simple `ISuspensionDriver`, similar to the WP8 and WinRT ones to get people started
- [ ] Fix all of the horrendously buggy Android code