Add sorting capabilities to the MultiColumnComboBox, similar to those of the Grid, where "sortable" enables sorting for the columns.

In the grouping demo for MultiColumnComboBox (https://demos.telerik.com/aspnet-mvc/multicolumncombobox/grouping), the first group 'Argentina' is not displayed as a black label on the right. This is inconsistent with the way other groups are displayed.

This can pose a usability issue for example when there are only two groups. The second group has a black label on the right, but the first group does not.

To be consistent, the first group should also display as a black label on the right.

Please consider adding a .Format() property to the columns for MCCB. It was a real pain to correctly format a date column of a sub template of another template. In most cases the grid control can use something like .Format("{0:dd/MM/yyy"}), but the MCCB must use template scripting. It took a while to get the scripting and escaping just right for it to work. Having a .Format() option would simplify things.