ComputerManager has a thread to run the CPU whenever its told to either
step or run. It can be told to stop the CPU too. Cycle count and keystate
feedback is available along with read-only of the computer from status()
Adds 'doom like' 3dviprmaze-vip for demo (VERY VERY SLOW)
updates egui interface to let user select from files in resources/roms
updates cargo to centralize dependencies
95 passing tests