Stack functionality

I added the Stack Pointer register, along with PUSH, POP, call and ret instructions. The stack grows downwards with frames of a WORD (32-bit). The SP starts at the top of RAM, PUSH moves it down four cells, POP moves it up four cells. Documentation hasn’t been changed fully.

Changes

Further, I removed the –menu option as it was mostly useless and added the –docs option to print out sections of the docs in the terminal.

The screenshot below showcases the output for -di