Enhancement: PTable sorting

[znicholasbrown]

PTable currently requires row sorting to be implemented downstream because the tables have no built-in sort methods.

I imagine sorting being based on column header, with the table / table header components exposing methods and models that would allow the consumer to control and respond to changes in the sort order. I think we can extend the TData model to include sort on the column, which would be a boolean that controlled whether sort interactions were enabled by default for the column.