now is enable build and delete towers in game and improve graphic perfomance

find and correct many-many bugs

towers.cpp

@@ -22,11 +22,9 @@ bool Towers::addTower(int playerId, int srcId, QPoint pos)
 		qCritical("ERROR out of towers range");
 		return false;
 	}
-	QRect alrec(pos,QSize(1,1));
+	QRect alrec(pos,QSize(2,2));
 	for (QHash<int, AlienType>::iterator i = gameData->curAliens.begin(); i != gameData->curAliens.end(); ++i)
-	{
 		if (alrec.contains((*i).pos.toPoint())) return false;
-	}
 	TowerType tw;
 	tw.src = srcId;
 	tw.imgType = gameData->players.at(playerId)->srcTowers.at(srcId).imgType;