Adds a new menu item at the given item.
        
        :param      newItem | <QTreeWidgetItem>
                    atItem  | <QTreeWidgetItem>

def addMenuItem( self, newItem, atItem ):
        """
        Adds a new menu item at the given item.
        
        :param      newItem | <QTreeWidgetItem>
                    atItem  | <QTreeWidgetItem>
        """
        tree = self.uiMenuTREE
        
        if ( not atItem ):
            tree.addTopLevelItem(newItem)
            
        elif ( atItem.data(0, Qt.UserRole) == 'menu' ):
            atItem.addChild(newItem)
        
        elif ( atItem.parent() ):
            index = atItem.parent().indexOfChild(atItem)
            atItem.parent().insertChild(index + 1, newItem)
        
        else:
            index = tree.indexOfTopLevelItem(atItem)
            tree.insertTopLevelItem(index + 1, newItem)