Parser for alu1short, alu2short, alu1reg, and alu2reg asm instruction forms.
Add comments to asm parser, and don't check for semicolons within parse_inst and its children.
Parse alu long and alu1 regsh instruction forms.
Update asm lexer/parser. Can now parse all instructions except branch and "other".
Support alu1long instructions in asm parser.
Instruction encoder, capable of encoding all forms of instructions that the parser can currently parse.