Simplification for Projects 4 and 5

I've decided to make a couple of simplifications of KURM09 for Projects 4 and 5.

First, you do not need to implement conditional instructions. Recall that conditional instructions (addc, subc, etc) only execute if the status register is non-zero and are no-ops otherwise. Thus, the only instruction that will look at the status register is bra and we covered that instruction in class. I don't think we've discussed them sufficiently in class for me to ask you to implement them and it should simplify the last two labs a bit.

Second, the status register will be updated after every instruction. This simply means that the status register is clocked and will never be disabled. Note that bra does not access the register file in any defined way. Thus, the contents of the status register can be any value after bra executes. In effect, status register values for the next state after bra are don't cares.

Hopefully these changes will simplify things by making the enable logic for the register file and the status register simpler. The status register is no longer involved in determining when the register file should be enabled and the status register is now always enabled.