[INTERNAL] moved file list classes and XMPP extensions to Core

Change-Id: Idb3087b9d6d6c1a86d50e1ea3c73f5b3e64f6ca3
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1734
Tested-by: Saros-Core QA
Tested-by: Saros-Eclipse QA
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>