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-Server-Patches/0321-Implement-World.getEntity-UUID-API.patch

@@ -1,28 +0,0 @@
-From 45b9aa46ba5547e98975dacc52a5caefffdc5721 Mon Sep 17 00:00:00 2001
-From: Brokkonaut <hannos17@gmx.de>
-Date: Tue, 3 Jul 2018 16:08:14 +0200
-Subject: [PATCH] Implement World.getEntity(UUID) API
-
-
-diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-index e2da30d88..210e3bc4e 100644
---- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-@@ -791,6 +791,14 @@ public class CraftWorld implements World {
-         return list;
-     }
- 
-+    // Paper start - getEntity by UUID API
-+    public Entity getEntity(UUID uuid) {
-+        Validate.notNull(uuid, "UUID cannot be null");
-+        net.minecraft.server.Entity entity = world.getEntity(uuid);
-+        return entity == null ? null : entity.getBukkitEntity();
-+    }
-+    // Paper end
-+
-     public void save() {
-     // Spigot start
-         save(true);
--- 
-2.16.1.windows.1
-