ForgeFlower is better than Spigots FernFlower at decompiling the source.
However, in order to maintain the CraftBukkit patches, we must keep
using spigots for the primary.
However, for any file that we import on top of Spigots imported files
there is nothing stopping us from using better decompiled files.
So these changes will use ForgeFlower to maintain a better set of
decomped files, so anything we add on top of Paper can start off
in a better spot.
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.
Aikar
Zach Brown