* Combines skill_cast_db, skill_castnodex_db, skill_copyable_db, skill_nonearnpc_db, skill_require_db, and skill_unit_db into skill_db.
* Introduces a cached YAML class for quicker lookups.
* General cleanups and optimizations.
* Includes CSV2YAML conversion tool.
Thanks to @Lemongrass3110!
Co-authored-by: Lemongrass3110 <lemongrass@kstp.at>