[CTFGUILD-85]: Change value of device_type from string to numeric value
Models changes:
* [CTFGUILD-88]: Character model should be dropped,
* [CTFGUILD-93]: Merge model Map with Game model,
* [CTFGUILD-89]: Team balancing,
* [CTFGUILD-90]: Add field 'team' in user model,
* [CTFGUILD-92]: Add fields: 'owner', 'last_modified', 'created' to model Game.