[Members] discussion list cleanup

[Peter Saint-Andre]

While doing a bit of admin on our mail server, I glanced at the roster 
of discussions lists: http://mail.jabber.org/mailman/listinfo

I think we can delete but archive the xmpp-commits list (last message 
May 2014, and not necessary now that people can watch via GitHub).

I also propose that we delete but archive jingle at xmpp.org and point 
discussion to the standards at xmpp.org list.

I'm on the fence about the security at xmpp.org list but I suppose it's 
fine to keep it around.

Peter