Adds comments to GameWrapper

[ubelhj]

Attempts to clarify meaning of some functions in the GameWrapper by elaborating what I've learned from writing plugins. If this is useful I can try and do this with more headers

[CinderBlocc]

Thanks for bringing this up. We've started discussing forms of documentation, but can't guarantee yet that we'll add any. Because this repo gets updated from an external source, we can't merge requests automatically, so I'll close this request.