Restructure the codebase

[HunterZ]

The UMoria codebase is rather messy, with very few headers, source files mixing internal and external functions, code files named "miscXYZ.c" etc.

Should maybe consider breaking the codebase up into subdirectories, possibly even building those into separate static libraries that get linked together at the end. This might help get better code/design separation between various areas of functionality. Maybe have a main header and source file for each module, backed up by headers and/or source files that are internal to that module?

As for the "misc" stuff: See if there are any themes that it can be sorted into, because "misc" is incredibly nondescript, and encourages chaos.