URBNG-35: Most functions of WebApi should be implemented now

I believe these functions works (somehow):
* get list of games sorted by distance to nearest game's gps task (if task exists)
* get game details
* list tasks
* get task details
* login
* register
* join game
* leave game
* get user game status (currently it's just sum of points and rank with fixed value for all users)
* get user task status (points, attempts, can reply - but user must send at least one solution to get his status)
* send answer for 2 types of tasks: quiz and gps

Still needs implement:
* task dependencies
* user rank
* notifications