Rename _view to _gameWindow.

Split MonoGameAndroidGameView out in to its own file and move Touch, KeyDown/Up, ISurfaceHolderCallback in with it.
Move a #if ANDROID hack from GamePlatform in to the AndroidGamePlatform
Tidy up licence header and usings in these files while I'm refactoring them.
Set Game.Activity from within the AndroidGameActivity to save user code from needing to do it. Un-[Obsolete] it as there are heaps of places that need access to it that don't have access to game (we could add it to the ServiceContainer but they'd need Game to get it)
This doesn't need to be a property
Move OrientationListener in to AndroidGameWindow. Make Game variable in a few places private so people don't try use it when they shouldn't.
Update the template Activity to work.