- changed the target database from mysql to postgresql
- so the db.table_prefix changed to db.struct.
- added getAll on Difficulties type
- renamed sekai-scores-db to sekai-meta
- add a new resource file, it will be the next song data storage method.
- add "id" field to Song, means the song id in game and wiki.
- add "id" field to Difficulty, it is a String of EASY/EXPERT etc.
- changes the parseJSONString implementation
- add song 夜に駆ける, complete the group SekaiSpecial