Refactor TAC.CodeGen, add features to MIPS.Language

I need to set this down now and do spimbot with it in its current form. As such, here is the TODO NEXT comment that I left in TAC.CodeGen to remind myself of what I was doing.

- I was busy refactoring all the code into the module to use generic
load and store instructions that handle moving data to/from memory locations.
- ~~Apparently, you can write lw $reg, name+offset when name is a label or an extern/lcomm'd
variable. MIPS.Language, Parser, Pretty, and PrettyTH should be modified to allow using this.~~
- ~~This refactor should take advantage of it.~~

- ~~integral{Load, Store}MemLocTypeWithDefault need to be adjusted for DataLocs.~~