Handle interactions between objects in a dedicated class

[chriskerrc]

Interactions between objects are not currently handled in a consistent way. For example, the snake eating food is handled in the Snake class. Instead, we should handle these interactions in a dedicated, central Interaction class, or similar.

[chriskerrc]

Move stuff into GameScreen class? Or split GameScreen class into rendering and object collision handling. Make new GameHandler class.

[chriskerrc]

Strategy: in GameScreen class, do all setup on GameScreen object. Then pass this object out to another GameManager class, which does the runtime stuff. The goal here is to keep the GameScreen class more clean, so it's only doing one thing.

[chriskerrc]

Making this low priority for now, because it doesn't affect user experience. Come back to this after the report is done and game bugs have been fixed.

[chriskerrc]

Won't do