[Galegroup] Fix Gale NewsVault. Add support for PDF/HTML attachments

I noticed that NewsVault was not working, so this fixes that.

I also added support for attaching PDF attachments, or if that's not available in the Gale Virtual Reference Library, it will attach HTML (not the page snapshot, but the HTML that you would be able to download from them of the article).

I think the only thing that I intentionally left out of the old translator is the proxifying of the URL field. This doesn't really make sense to me (unless I was misreading the code), since the URL field is meant to be citable and proxied URLs are clearly not (although Gale URLs are not stable anyway, so maybe there's no point in keeping a URL link at all).

I've tested this with both Gale NewsVault and Gale Virtual Reference Library (I don't think I have access to other Gale resources if they exist) and it seems to work quite well. It would be great if someone can run a couple tests from their end.