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.
This will force the saves to spread over multiple ticks even when many
players auto save interval is aligned, avoiding spikes on large servers.
Closes#1021
Spigot has patched this issue inside MapIcon, meaning that we no longer need to maintain this patch; Spigots patch also fixes#668 in that it will verify the length of the array, as well as protect against a negative type value being fetched from the array. Only real change is that Spigots patch returns a MapIcon.Type.PLAYER, instead of the RED_MARKER as originally PR'd by Aikar.
