Portray to HTML

[JanWielemaker]

We need a way to make print/1, calling portray/1 to display terms as HTML instead of plain text. For example:

html_portray(Link) :-
    is_uri(Link),
    html(a(href(Link), Link).

[Anniepoo]

Would it be good if this was somehow done uniformly with the 'render' directive in SWISH?