Code refactoring

- Code refactoring
- Fix a bug that the other player will not become the host of the room at once, when the player disconnect in link play.

> Maybe add many unknown bugs. XD
> The song database `arcsong.db` will not used in the future. You can use a tool in `tool` folder to import old data.

latest version/api/api_auth.py

@@ -2,7 +2,7 @@ import hashlib
 import base64
 import time
 import random
-from server.sql import Connect
+from core.sql import Connect
 import functools
 from setting import Config
 from flask import jsonify