[FIX] #678 Choose only one "XMPP ID" vs "Jabber ID" 

The service is called XMPP and not Jabber.
An XMPP address is called (for historical reasons, see RFC)
Jabber Identifier (JID) and not XMPP-ID.

Change-Id: Icc882e0ebd8803ce241820c2ce4b7d5fa1bb3c48
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1401
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>