[INTERNAL] removed version check from the network layer

It is up to the application to ensure that the received data matches the
required version. The version ID for Saros extensions is now included in
the extension itself and no longer put into the packet ID field.

TODO: move all Saros extensions out of the network layer

Change-Id: I3064ed57400f4d914e65d7c6f846d51bcdf91661
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/960
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>