Added GeneralConstants file

src/classes/GeneralConstants.php

@@ -0,0 +1,31 @@
+<?php
+
+/*
+
+           -
+         /   \
+      /         \
+   /   PocketMine  \
+/          MP         \
+|\     @shoghicp     /|
+|.   \           /   .|
+| ..     \   /     .. |
+|    ..    |    ..    |
+|       .. | ..       |
+\          |          /
+   \       |       /
+      \    |    /
+         \ | /
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+
+*/
+
+//Gamemodes
+define("SURVIVAL", 0);
+define("CREATIVE", 1);
+define("ADVENTURE", 2);