Revision 606

Fix assert calls.
(ClassGrid._OnCellDClick): Call up to the classifier to open the
        dialog to edit the groups properties.
(ClassGrid._OnCellResize): Make sure that the scollbars are drawn
        correctly if a cell is resized.
(ClassTable.SetClassification): New. Changes the classification
        that is in the table.
(ClassTable.__SetRow): Allow groups to be prepended.
(Classifier): New code for opening the EditProperties and
        GenerateRanges dialogs.
(SelectPropertiesDialog.__GetColor): Only set the color in the
        color dialog if the current color is not None.