Current Chunk for Entity and Block Entities, counts by entity type

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.

Spigot-API-Patches/0124-Entity-getChunk-API.patch

@@ -0,0 +1,34 @@
+From 99dd52878fbaede269af3c5cf38c179688506099 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Wed, 4 Jul 2018 02:25:48 -0400
+Subject: [PATCH] Entity#getChunk API
+
+Get the chunk the entity is currently registered to
+
+diff --git a/src/main/java/org/bukkit/entity/Entity.java b/src/main/java/org/bukkit/entity/Entity.java
+index 3ae4de7a..e2a2b78c 100644
+--- a/src/main/java/org/bukkit/entity/Entity.java
++++ b/src/main/java/org/bukkit/entity/Entity.java
+@@ -1,5 +1,6 @@
+ package org.bukkit.entity;
+ 
++import org.bukkit.Chunk;
+ import org.bukkit.Location;
+ import org.bukkit.EntityEffect;
+ import org.bukkit.Nameable;
+@@ -514,5 +515,12 @@ public interface Entity extends Metadatable, CommandSender, Nameable {
+      * @return True if entity spawned from a mob spawner
+      */
+     boolean fromMobSpawner();
++
++    /**
++     * Gets the latest chunk an entity is currently or was in.
++     *
++     * @return The current, or most recent chunk if the entity is invalid (which may load the chunk)
++     */
++    Chunk getChunk();
+     // Paper end
+ }
+-- 
+2.18.0
+