Deep refactoring around the WindowManager class

Previous WindowManager functionality goes to the following new classes:
- ApplicationRegistry;
- PopupRegistry;
- ScreenContentManager;
- TileManager;
- TileVisitor;
- Window.

The following class is added:
- InstanceManager.

The following classes go to separate files:
- ReviewModeArea;
- InitialEventLoopStopCondition;
- EventQueue;
- PopupEventLoopStopCondition.