Now it's up to 99% tests passing, 15362 are still failing, but many
of those are the unimplemented IN/OUT instructions, which the Genesis
doesn't seem to use
Special thanks to raddad772 https://github.com/raddad772
Also added some fixes to the Z80 for panicking math operations, but
it still won't complete due to an unimplemented instruction
I wanted to make this a bit more modular, so it's easier in theory to
write external crates that can reuse bits, and selectively compile in
bits, such as adding new systems or new cpu implementations
