Custom styling for Data View items

The basic implementation of data views relies on the underlying toolkit to provide styling when displaying an item based on the type of the item's editor value.

We would like to provide a hook where users can provide their own styling information, such as font selections, cell borders, and column widths.

This should be a feature of the view, rather than the model, so that different views of the same model can choose to display in different styles (or not, as appropriate).