Add a custom shutdown message set in bukkit.yml. Addresses BUKKIT-3031

By: feildmaster <admin@feildmaster.com>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -930,6 +930,10 @@ public final class CraftServer implements Server {
         return configuration.getInt("settings.spawn-radius", -1);
     }
 
+    public String getShutdownMessage() {
+        return configuration.getString("settings.shutdown-message");
+    }
+
     public int getSpawnRadius() {
         return ((DedicatedServer) console).propertyManager.getInt("spawn-protection", 16);
     }

paper-server/src/main/resources/configurations/bukkit.yml

@@ -24,6 +24,7 @@ settings:
     connection-throttle: 4000
     query-plugins: true
     deprecated-verbose: default
+    shutdown-message: Server closed
 spawn-limits:
     monsters: 70
     animals: 15