Closes#1197
While this really undoes a lot of the desired performance gains avoiding chunk lookups,
we sadly have to accept this because we are seeing lots of bugs with entities.
This enables us a fast reference to the entities current chunk instead
of having to look it up by hashmap lookups.
We also store counts by type to further enable other performance optimizations in later patches.
CraftBukkit removed their implementation that caused this issue,
switching to Mojang's implementation which doesn't appear to share it. I
already removed the important bit in the last upstream merge, this is
just unused and unnecessary now. So we remove it.
