Commodore 64 Raspberry Pi Conversion additional ports

I made a few modifications to the original models by https://www.thingiverse.com/thing:2852922.

Changes:

1) the bracket that goes over the cartridge port now has a space for both a USB port, and an Audio jack. (You'll need to drill the holes for the screws on the USB port).
2) the bracket over the user port had a few small tweaks to make them line up with the screw post (at least on my machine) and to help it snap in easier, and I made the holes go all the way through for the port mounts.