Implement logical operations.
Implement the rest of the arithmetic ops. This implements subtraction, multiplication, and division, as well as the associated checks for overflows and div by 0
Implemented addition and the generalised parts of handling arithmetic ops. In particular, implemented the invert (I) flag, and ensured that the program counter is unwritable for arithmetic instructions.
Initial commit Creates processor.rs as well as the processor struct and the start of the code for executing instructions.