Add support for some Bugzilla instances. This support currently requires that
the JSON-RPC interface is available at bugzilla.organization.{com|org|net}/jsonrpc.cgi.

It is known to work with with Wikimedia, Mozilla, KDE, and Redhat.
It is known *not* to work with GNOME, Kernel.org, and Novell.
Tighten up the identification of lp bugs.