When a class implementing Action returns a string from getUrlName(), the link
that is rendered in the list to the left always has a trailing slash, even
though I didn't supply one in the URL. This causes problems when adding an
action linked to a specific file rather than a path on a site.

For example, if MyAction.getUrlName() returns "http://foo.com/bar.html" to go to
a specific file in a site, the extra slash gets added and relative URL's in that
HTML file no longer work.

Since URL's are allowed to include a filename, one should be able to return a
specific file from getUrlName() without it always being treated like only a path.