Can SQL kernel output other MIME types besides a Jupyter widget?

I see that the SQL kernel outputs its data only as a MIME type `application/vnd.jupyter.widget-view+json`, which corresponds to a Jupyter widget.

Jupyter messages from other kernels often appear with multiple MIME types to allow different display options--for example, a Pandas dataframe by default comes with `text/html` and `text/plain`.

I'm wondering if the SQL kernel can be configured to output any other raw data formats? I'm especially thinking about the [Tabular Data Resource](https://frictionlessdata.io/specs/tabular-data-resource/) format, which would allow the data to be consumed by the [nteract Data Explorer](https://github.com/nteract/nteract/tree/master/packages/data-explorer).

Start by tracing how the SQL kernel publishes its Jupyter widget-view MIME output and compare it with the multiple MIME types used by other kernels. Check whether Tabular Data Resource output could meet the nteract Data Explorer requirements; done means establishing a supported configuration or a clearly scoped implementation path.

Written by the indexing model from the issue text.