Added Server.getServerId() for ID purposes.

By: sk89q <the.sk89q@gmail.com>

paper-api/src/main/java/org/bukkit/Server.java

@@ -63,6 +63,14 @@ public interface Server {
      */
     public String getServerName();
 
+    /**
+     * Get an ID of this server. The ID is a simple generally alphanumeric
+     * ID that can be used for uniquely identifying this server.
+     *
+     * @return The ID of this server
+     */
+    public String getServerId();
+
     /**
      * Broadcast a message to all players.
      *