Bigger Chunks

[olls]

Linking to #64, we should probably increase the chunk size. Because we read a file whenever we load a chunk, we should try to make that happen as little as possible. I can't see any reason why we shouldn't increase the chunk size to at least 4x or even 8x.

[olls]

Maybe we also want to decouple the 'chunk' file size from the game chunk size, if bigger chunks turn out to be harder for the game to deal with. That way we still get the advantages of the less often file loading.