[Request] Images on Gamepad and Live Remapping

[CuantumQ]

Two requests that tie together neatly.

Request 1: Ability to set an image in usendmii that fills the Gamepad Screen once connected instead of the usendmii menu. People could either use this for decoration or to make it more clear where they should click on the screen if they have many screen regions.

Request 2: The ability to swap between control mappings while usendmii is running, possibly through an input in usendmii. This could make it more convenient to change through control mappings. And if combined with the first Request, the Gamepad could change images to show what mapping you're currently using.