remove useless import

[bugall]

No description provided.

[what-the-diff]

• server.js
  • comment out the code of app and server, which is used to start a http service
• dbConnection.js
  • change host to psm in mysql configs; add idlTime: 10 for connection pooling configuration (default value is 8)
• log4js configure file has been changed from 4 files into 1 file with different categories(info/warn/error/fatal). The default category will be info level logging if no specific category was specified when calling getLogger() function; also remove all other categories except 'default' and 'info'. This means that only one logger instance can be created by using this library now instead of four instances before refactoring happened on it's configure file

[bugall]

/wtd explain