Initial Paper-API for Bukkit 1.13 Preview 4 - THIS IS NOT SERVER

This branch/commit is only useful to those who purely use a clean Bukkit/Spigot/Paper API
and does not use NMS/OBC references.

This will let you start updating your plugin to the latest 1.13 builds of Bukkit Preview (4 as of now)

Note that this release is not final!!! API breakages may occur!

It is up to you if you find use out of this work.

pre/Bukkit-Patches/0017-Add-support-for-fetching-hidden-players.patch

@@ -0,0 +1,28 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Tux <write@imaginarycode.com>
+Date: Sun, 9 Feb 2014 14:02:11 -0500
+Subject: [PATCH] Add support for fetching hidden players
+
+
+diff --git a/src/main/java/org/bukkit/entity/Player.java b/src/main/java/org/bukkit/entity/Player.java
+index e021495e..5c55c2e2 100644
+--- a/src/main/java/org/bukkit/entity/Player.java
++++ b/src/main/java/org/bukkit/entity/Player.java
+@@ -0,0 +0,0 @@ public interface Player extends HumanEntity, Conversable, CommandSender, Offline
+         {
+             throw new UnsupportedOperationException( "Not supported yet." );
+         }
++
++        /**
++         * Gets all players hidden with {@link #hidePlayer(org.bukkit.entity.Player)}.
++         *
++         * @return a Set with all hidden players
++         */
++        public java.util.Set<Player> getHiddenPlayers()
++        {
++            throw new UnsupportedOperationException( "Not supported yet." );
++        }
+     }
+ 
+     @Override
+--