Allow specifying a custom "authentication servers down" kick message

Thanks to @phenomax in #855

Spigot-Server-Patches/Allow-specifying-a-custom-authentication-servers-dow.patch

@@ -0,0 +1,44 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Riley Park <rileysebastianpark@gmail.com>
+Date: Thu, 17 Aug 2017 16:08:20 -0700
+Subject: [PATCH] Allow specifying a custom "authentication servers down" kick
+ message
+
+
+diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+index f4b23703..f5cb9799 100644
+--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
++++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+@@ -0,0 +0,0 @@
+ package com.destroystokyo.paper;
+ 
++import com.google.common.base.Strings;
+ import com.google.common.base.Throwables;
+ 
+ import java.io.File;
+@@ -0,0 +0,0 @@ public class PaperConfig {
+     private static void suggestPlayersWhenNull() {
+         suggestPlayersWhenNullTabCompletions = getBoolean("settings.suggest-player-names-when-null-tab-completions", suggestPlayersWhenNullTabCompletions);
+     }
++
++    public static String authenticationServersDownKickMessage = ""; // empty = use translatable message
++    private static void authenticationServersDownKickMessage() {
++        authenticationServersDownKickMessage = Strings.emptyToNull(getString("messages.kick.authentication-servers-down", authenticationServersDownKickMessage));
++    }
+ }
+diff --git a/src/main/java/net/minecraft/server/LoginListener.java b/src/main/java/net/minecraft/server/LoginListener.java
+index c5434e6b..75df9283 100644
+--- a/src/main/java/net/minecraft/server/LoginListener.java
++++ b/src/main/java/net/minecraft/server/LoginListener.java
+@@ -0,0 +0,0 @@ public class LoginListener implements PacketLoginInListener, ITickable {
+                             LoginListener.this.i = LoginListener.this.a(gameprofile);
+                             LoginListener.this.g = LoginListener.EnumProtocolState.READY_TO_ACCEPT;
+                         } else {
++                            // Paper start
++                            if (com.destroystokyo.paper.PaperConfig.authenticationServersDownKickMessage != null) {
++                                LoginListener.this.disconnect(new ChatComponentText(com.destroystokyo.paper.PaperConfig.authenticationServersDownKickMessage));
++                            } else // Paper end
+                             LoginListener.this.disconnect(new ChatMessage("multiplayer.disconnect.authservers_down", new Object[0]));
+                             LoginListener.c.error("Couldn\'t verify username because servers are unavailable");
+                         }
+--