Change error! to panic
Simplify JP <flag>, n calls
Fix CCF instruction
Change Add's ZeroFlag behavior to mimic increment. When the register rolls over to 0 then ZeroFlag should be set.
Modify subtract to be in line with add and increment. ZeroFlag is set on rollover and zero result
Modify GameboyMemory to properly handle writes and reads
Change zeroflag in shift and rotate instructions
Small cleanup
Remove feature gate
Fix some opcodes
Changes to allow compilation with latest rust