driver: verify message body of incoming messages
driver: verify message body of incoming messages

We need to verify all the incoming data, and add any string or path
arguments to our MatchFilter. For now only verify the signature,
the body will be checked in a follow-up commit.

Signed-off-by: Tom Gundersen <7c8224529a7c718e876cb2496c973509fde1e50e@jklm.no>

bus1/dbus-broker