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/0176-Add-PlayerPostRespawnEvent.patch

@@ -0,0 +1,67 @@
+From f38ffb6d09efb22ea0368e835ed6c4c0fec23773 Mon Sep 17 00:00:00 2001
+From: MisterVector <whizkid3000@hotmail.com>
+Date: Fri, 26 Oct 2018 21:33:13 -0700
+Subject: [PATCH] Add PlayerPostRespawnEvent
+
+
+diff --git a/src/main/java/com/destroystokyo/paper/event/player/PlayerPostRespawnEvent.java b/src/main/java/com/destroystokyo/paper/event/player/PlayerPostRespawnEvent.java
+new file mode 100644
+index 00000000..31f34b54
+--- /dev/null
++++ b/src/main/java/com/destroystokyo/paper/event/player/PlayerPostRespawnEvent.java
+@@ -0,0 +1,52 @@
++package com.destroystokyo.paper.event.player;
++
++import org.bukkit.Location;
++import org.bukkit.entity.Player;
++import org.bukkit.event.HandlerList;
++import org.bukkit.event.player.PlayerEvent;
++import org.jetbrains.annotations.NotNull;
++
++/**
++ * Fired after a player has respawned
++ */
++public class PlayerPostRespawnEvent extends PlayerEvent {
++    private final static HandlerList handlers = new HandlerList();
++    private final Location respawnedLocation;
++    private final boolean isBedSpawn;
++
++    public PlayerPostRespawnEvent(@NotNull final Player respawnPlayer, @NotNull final Location respawnedLocation, final boolean isBedSpawn) {
++        super(respawnPlayer);
++        this.respawnedLocation = respawnedLocation;
++        this.isBedSpawn = isBedSpawn;
++    }
++
++    /**
++     * Returns the location of the respawned player
++     *
++     * @return location of the respawned player
++     */
++    @NotNull
++    public Location getRespawnedLocation() {
++        return respawnedLocation.clone();
++    }
++
++    /**
++     * Checks if the player respawned to their bed
++     *
++     * @return whether the player respawned to their bed
++     */
++    public boolean isBedSpawn() {
++        return isBedSpawn;
++    }
++
++    @Override
++    @NotNull
++    public HandlerList getHandlers() {
++        return handlers;
++    }
++
++    @NotNull
++    public static HandlerList getHandlerList() {
++        return handlers;
++    }
++}
+-- 
+2.21.0
+