WIP: Working on GooglePlay games services

- implemented achievement handling (show achievements, unlock
  achievement, increment achievement)
- but not stable yet (achievements popup not shown each time,
  sometimes application hangs on achievement unlock)
#1: Try to fix problems with incrementAchievement and unlockAchievement

- we try to preload achievements info for incrementAchievement work properly
Implement showLeaderboard and submitScore
Implement AppStateClient support

- and refactore code a bit
Add example of usage of GooglePlay
Merge branch 'dev'