[Input] Add IsAnyKey/ButtonDown/Pressed to input state.

Adds properties to KeyboardState, MouseState, JoystickState and GamePadState
(GamePadButtons), to see if any key or button is down. This should be faster
than iterating over all the public IsDown properties as we can make use of the
internal bit fields.

GamePadButtons uses IsButtonPressed rather than IsButtonDown like the others as
it more closely matches it's current interface (no down methods).