added the first 3 opcodes to the CPU. Before going further, going to add
the display to see if things are changing correctly - which means taking
my hand at executing too...also, I am starting to see the need to break
this up into a bunch of little functions, as with 3 opcodes I already
coded 2 very similar blocks... not good for sanity, readability, or
anything...must be changed, but first, get it working ;)