Started sprite rendering code...
Added color palette code - subject to change :s
Updated: -
- cpu/instructions.go = RST and STOP instructions had incorrect settings
  for the number of operands
- cpu/z80.go = Started adding support for interrupts in cpu Step. Fixed
  some dodginess around the way stack pushing/popping was written.
- debugger.go = Made the debugger a lot simpler and nicer to use.
  Removed a lot of useless cruft
- gbc.go = Added some additional features to the machine so you can boot
  in debug mode, skip the boot screen etc
- gpu/gpu.go = started adding some support for recognising when the
  window registers have been updated
- inputoutput/inputoutput = small tweaks to where the screen is
  positioned
- mmu/Peripheral.go = Added a new method so all implementers of the
  Peripheral interface have a reset method
- mmu/mmu.go = Added support for interrupts
- utils/utils.go = added some more utility functions, mainly for strings