Added TileGrid class, based on House of Shadows TileGrid.
Added FreshGame for game-related features that are not general enough for FreshScene2D.

Refactored TileGrid to use Grid2.
Adapted House of Shadows Lighting for FreshGame.
Added XML and folder structure guidance for FreshScene2D and FreshGame.
Re-added LightBlocker concept.
Added actor class.
Basic player physics implemented.