Kinda a mixed bag of things

I wanted to fix the fact that hitting a joystick direction updates the sprite
position once every host frame, instead of every emulated frame. Instead, I:

- Swapped left and right in the joystick, to the correct way around;
- Consolidated frame-state into the "owner" of the computer;
- Added color RAM read/write to the MMU;
- Moved the initial screen into the game kernel.