Consoles

This adds a new level to the navigation stack. It separates out roms into their own Consoles so you can browse by console.

Kart now starts by showing you a list of your valid consoles, picking one will show you it's roms, and pressing `ESC` will bring you back to the list of consoles.

Console images are set by adding a banner image named `image.png` to the console's directory.