Implement several more world methods

I have tested all of these methods except `getBiome` and `setSeed`

I'm not sure about the `getBiome` method and so it could be removed if it's not going to work

There are some comments which it'd be good to have some input on
This doesn't compile, see https://travis-ci.org/SpongePowered/Sponge/builds/45614519#L514-L517