<link> URLs are tracked and shouldn't be

If you use in a mailing template, for example to load a webfont, that URL is converted to a tracked URL. Presumably it shouldn't be as this makes a mess of the clickthrough statistics (every one of these links will be counted as clicked as long as the user's mail client fetches the resource). In other words, a link being fetched in a not a click and shouldn't be counted as one.

Do we need to track any URLs that aren't inside an <a> tag? It might be easier to limit to <a... rather than trying to exclude <link.... The only valid way to write an <a> is with the tag right after the <, so I think we could just look for <a instead of <.

I can provide a patch if this approach is supported.