Step commit

Step works! Kernel handles the execution now, so it will execute based
on whether step is enabled or not. If it is enabled, it will not execute
until you manually step through.

All requirement should now be met:
Modify load command - done
add run command -done
execute program - done
update registers - done
display PCB at end of execution - done (using the trace)
single step - done
pcb - done
memmanager - done
mainmem -done
cpu enhancements - done