Dedicated Shield / Super Transformation Button

This merge request adds a new button, called "Shield". Press the Shield button midair to perform the shield ability of whatever shield you have. If you're able to turn super, press it while grounded or while midair without a shield to transform. You can also detransform by pressing the Shield button while super.

The advantages of this are letting you perform air spin abilities without being interrupted by shield abilities or needing to disable them, letting you transform into super even with a shield, as well as letting you detransform from super whenever you like.

As for default bindings, the Shield button is simply on Left Alt for keyboards by default. On controller, however, things needed to be moved around a little to work better. Firstly, Shield is binded to the Left Bumper. The first person toggle, which used to be on the Left Bumper, has now been moved to D-Pad Down. The Score or "Tab" screen button, which used to be on D-Pad Down, has now been moved to Back/Select. And Screenshot, which used to be on Back/Select, has been removed entirely from the default bindings for controller, as it serves no gameplay function.

Test exe: shieldbutton4.exe