* Renamed `ml` to `master_level`
* Added `ultimate_mastery` to Jobs and Parties
* Restructured `atk`, `hp`, `max_level`, and `max_skill_level` and other relevant attributes under a `stats` field on canonical objects
* Refactored and tried to simplify methods in PartiesController
* Implemented new error render methods in ApiController
* Removed parties/[weapons, summons, characters] routes