Create ChoiceScreen class
Refactoring

- Move ChoiceScreen and MainClass to TextInterface.cs, inside TextUi
  namespace
- Rename MainClass to MainScreen
- Minimal implementation in Main.cs
Partially implement class screen
Introduce IPersistenceService and refactor XMLDatabase
Implement hooks in ChoiceScreen
Clearscreen in ChoiceScreen
Remove Message in ChoiceScreen, favoring hooks
Minor refactoring
More hooks
Make Class not inherited from Identity
Various changes in TextInterface.cs
Project settings
New constructor for Manager for persistence
New Identity implementation based on attributes and reflection
Use the new Identity implementation
Fix some test cases
Doc for the new Identity class
Update Main