UI for gamifcation & stats

There is a some ideas about gamification and we have some icons but the current UI is not sufficient enough. We need a complete redesign.

• Revisit paper prototype and improve the paper prototype (ask Oliver for details)
• Add an onboarding to the badge case
• Add stats to paper prototype
• Where should be the entry point?
• How to inform users about the gamification elements?
• Does the paper prototype fits to Letterbox?
• Create an abstraction for logic
• Create new views

The logic for gamification and stats is sometimes incorrect or missing (Issue #172)