Support the Xbox 360 controller.

To switch betweeen the two adapters, press either Left Control on the
keyboard or the Start button on the Xbox 360 controller. Also, X on the
controller is the restart button.
Forgot to commit the actual adapter.
Merge branch 'master' into x360-input
Merge branch 'master' into x360-input

Conflicts:
	PuzzlePathDimension/Menus/GameplayScreen.cs
Add Context and Pause inputs, and a Connected property.
Merge branch 'master' into x360-input
Remove the old functionality of the Back button.

Also, hard-code the X button to do a restart of the level.
Add IsButtonDown() and IsButtonUp().
Remove a random print statement.
Remove more 'blah's in the code.
Merge branch 'master' into x360-input

Conflicts:
	PuzzlePathDimension/Menus/GameplayScreen.cs
	PuzzlePathDimension/PuzzlePathDimension.csproj
	PuzzlePathDimension/ScreenManager.cs