Generate enum-based battle constants at build-time

[lhearachel]

This makes use of a subproject that I wrote for generating constants files from a basic manifest schema. The goal here is to support having a single source of truth for such definitions that can be utilized by both the compiler and a direct assembler invocation for building data files (which we will need for battle scripts). The assembler does not support reading enum definitions out-of-the-box, so these definitions would need to either be:

1. Duplicated, and thus separately maintained
2. Moved to #define syntax, which is less-than-ideal for self-documentation of function signatures
3. Generated from a separate source-of-truth

[mid-kid]

My only complaint is that nobody is gonna be able to find the source of truth through neither their IDE nor a simple grep. This is because you took away their prefixes in the definitions files, which I think is a questionable feature.

Either:

• Write the constant names out in full without transforming them. Yes it's more verbose, but it's also easier to deal with.
• Output a comment at the top of the header telling the reader that it's a generated file, what program it was generated with, what file the constants originate from, and if relevant the command line arguments passed to the program.

Or both, preferably both.

[lhearachel]

Or both, preferably both.

I decided both was worthwhile, too.