Add wrapping classes for the Protobuf reply messages

This gives an easy interface without the need to deal with all the
protobuf specific stuff in the other modules.

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Compile cpp files in the messages subdir

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>