Relocated all file system utility routines from fs_main.c and sys_reslocator.c into (new) fs_util.c
fs_main.c's findLumpFile can utilize F_CheckLumpNumForName and F_FindFileForLumpNum when searching the lump directory mappings rather than implement the same logic again.
Updated names for various routines in fs_main.c (standardize)
Cleanup continues:
sys_reslocator.c into (new) fs_util.c
F_FindFileForLumpNum when searching the lump directory mappings
rather than implement the same logic again.