Start reworking of unit tests

* Instead of testing code against one register/memory state,
  I have tried to introduce multiple states. I did have HL
  flags change on opcode 0x21, but removed this as it increased
  test time for just the opcode from < 4 seconds, to well over
  2 minutes (and the HL flgas were written over anway). Only the
  PC is incremented now..
* Set CK_DEFAULT_TIMEOUT to 600 seconds. I will probably decrease
  this