0.1 - Basic features

This should fully implement basic assembly language. Supports identifiers, four pseudo-instructions related to those, the data segment, direct access to memory mapped IO. No support for bytes or other widths other than word.

https://docs.google.com/document/d/1AN-uqAFlSWyhOYCu5r69SF4dksxHxVPF_hEuQTsxCZg/edit?usp=sharing