Move version command update checking to the implementation

This makes it easier for downstream projects (forks) to replace the
version fetching system with their own. It is as simple as implementing
an interface and overriding the default implementation of
org.bukkit.UnsafeValues#getVersionFetcher()

It also makes it easier for us to organize things like the version
history feature.

Lastly I have updated the paper implementation to check against the site
API rather than against jenkins.

Spigot-API-Patches/0118-Entity-getChunk-API.patch

@@ -0,0 +1,36 @@
+From 510847f2f98f230e51cd206db7175a8b07f15b67 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 35d0909b..adca48f1 100644
+--- a/src/main/java/org/bukkit/entity/Entity.java
++++ b/src/main/java/org/bukkit/entity/Entity.java
+@@ -3,6 +3,7 @@ package org.bukkit.entity;
+ import java.util.List;
+ import java.util.Set;
+ import java.util.UUID;
++import org.bukkit.Chunk; // Paper
+ import org.bukkit.EntityEffect;
+ import org.bukkit.Location;
+ import org.bukkit.Nameable;
+@@ -624,5 +625,13 @@ public interface Entity extends Metadatable, CommandSender, Nameable, Persistent
+      * @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)
++     */
++    @NotNull
++    Chunk getChunk();
+     // Paper end
+ }
+-- 
+2.21.0
+