[INTERNAL] added packet extension for versioning

This packet extension should be more flexible than the old one and so
there should no need to break backward compatibility anymore.

Change-Id: Ia140c9e50d392181428a3fc19c80a2b2a6d770df
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1276
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>