Multi-domain XMPP/Jabber server support (GTalk)

This adds support for using a e.g. GTalk account to send the notifications.
Of course will work with any other XMPP/Jabber service that uses different server name than the part after the @ in the JID.

Also tested for sending notifications to yourself.
Let's hope Google doesn't kill XMPP client access any time soon. :-/