[packagekit] Convert the UpdateDetail::url field into UpdateDetail::{vendor_url, bugzilla_url, cve_url}

[Richard Hughes]

Guys,

As discussed, I've split up the UpdateDetail:url into vendor_url,
bugzilla_url, cve_url with the format <url>;<title>, where title can be
omitted if not known, and where none of the urls are actually required.

Tim, could you fix up the yumBackend.py please, and Matthias - please
could you do the gnome-packagekit bits. I think I've done enough to make
it compile and work, although it need a python legend now. :-)

Cheers lads.