DataTable expander cell should be customizable

[domehead100]

We sometimes use the expander feature on the DataTable for displaying a form inline for editing a row. In this case a different icon is desired other than the default, but there is no way to customize the rendering of the cell when expander=true. If we pass in a body prop, it is ignored. We've worked around this by overriding the CSS for specific DataTable instances, but there's more...

While you can show or hide the expander icon altogether by setting expander dynamically using a callback or expression, there's no way to show it but, for example, in a disabled state with a title or tooltip explaining to the user why they can't expand (edit) the row.

It would be nice if we were able to specify a custom template even for an expander column.

Note: we're currently using v1.4.1.