Guild PQ + fixed negative EXP error

Implemented Guild PQ. Fixed a problem introduced earlier where negative
EXP would be deemed as "integer overflow", provoking many game breaking
issues as result.

src/scripting/quest/QuestScriptManager.java

@@ -148,6 +148,7 @@ public class QuestScriptManager extends AbstractScriptManager {
 	public void dispose(QuestActionManager qm, MapleClient c) {
 		qms.remove(c);
 		scripts.remove(c);
+                c.getPlayer().setNpcCooldown(System.currentTimeMillis());
 		resetContext("quest/" + qm.getQuest() + ".js", c);
 	}