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-Server-Patches/0298-Add-More-Creeper-API.patch

@@ -1,78 +0,0 @@
-From 7f389a7f31a6f26910ff135b6c4cf67b376a36bb Mon Sep 17 00:00:00 2001
-From: BillyGalbreath <Blake.Galbreath@GMail.com>
-Date: Fri, 24 Aug 2018 11:50:26 -0500
-Subject: [PATCH] Add More Creeper API
-
-
-diff --git a/src/main/java/net/minecraft/server/EntityCreeper.java b/src/main/java/net/minecraft/server/EntityCreeper.java
-index 29569805cb..0c2c3c7308 100644
---- a/src/main/java/net/minecraft/server/EntityCreeper.java
-+++ b/src/main/java/net/minecraft/server/EntityCreeper.java
-@@ -13,7 +13,7 @@ public class EntityCreeper extends EntityMonster {
-     private static final DataWatcherObject<Boolean> POWERED = DataWatcher.a(EntityCreeper.class, DataWatcherRegistry.i);
-     private static final DataWatcherObject<Boolean> d = DataWatcher.a(EntityCreeper.class, DataWatcherRegistry.i); private static final DataWatcherObject<Boolean> isIgnitedDW = d; // Paper OBFHELPER
-     private int bz;
--    private int fuseTicks;
-+    public int fuseTicks; // Paper - public
-     public int maxFuseTicks = 30;
-     public int explosionRadius = 3;
-     private int bD;
-@@ -201,6 +201,7 @@ public class EntityCreeper extends EntityMonster {
-         return super.a(entityhuman, enumhand);
-     }
- 
-+    public void explode() { this.eb(); } // Paper - OBFHELPER
-     private void eb() {
-         if (!this.world.isClientSide) {
-             Explosion.Effect explosion_effect = this.world.getGameRules().getBoolean("mobGriefing") ? Explosion.Effect.DESTROY : Explosion.Effect.NONE;
-@@ -252,8 +253,19 @@ public class EntityCreeper extends EntityMonster {
-         return (Boolean) this.datawatcher.get(EntityCreeper.d);
-     }
- 
-+    // Paper start
-+    public void setIgnited(boolean ignited) {
-+        if (isIgnited() != ignited) {
-+            com.destroystokyo.paper.event.entity.CreeperIgniteEvent event = new com.destroystokyo.paper.event.entity.CreeperIgniteEvent((org.bukkit.entity.Creeper) getBukkitEntity(), ignited);
-+            if (event.callEvent()) {
-+                this.datawatcher.set(EntityCreeper.d, event.isIgnited());
-+            }
-+        }
-+    }
-+
-     public void dY() {
--        this.datawatcher.set(EntityCreeper.d, true);
-+        setIgnited(true);
-+        // Paper end
-     }
- 
-     public boolean canCauseHeadDrop() {
-diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftCreeper.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftCreeper.java
-index 796ee9e40d..2d38823c57 100644
---- a/src/main/java/org/bukkit/craftbukkit/entity/CraftCreeper.java
-+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftCreeper.java
-@@ -78,4 +78,22 @@ public class CraftCreeper extends CraftMonster implements Creeper {
-     public EntityType getType() {
-         return EntityType.CREEPER;
-     }
-+
-+    // Paper start
-+    public void setIgnited(boolean ignited) {
-+        getHandle().setIgnited(ignited);
-+    }
-+
-+    public boolean isIgnited() {
-+        return getHandle().isIgnited();
-+    }
-+
-+    public int getFuseTicks() {
-+        return getHandle().fuseTicks;
-+    }
-+
-+    public void explode() {
-+        getHandle().explode();
-+    }
-+    // Paper end
- }
--- 
-2.21.0
-