Introduce Achievement Management 🏆

[bitbrain]

Introduce a new class called AchievementManager which can be accessed on the GameContext.

The responsibility of this class is to register achievements and measure progress. The manager itself has different "storage" implementations for the state:

• DefaultAchievementConfiguration active by default
• AndroidAchievementConfiguration (based on GooglePlay)

Each AchievementConfiguration provides UI handling and persistence of state respectively. This handler can be configured on the BraingdxGame itself via the super constructor:

public MyGame(AchievementConfiguration configuration) {
   super(configuration);
}

This allows people to provide custom configuration for different platforms.