--help should say which settings are defaults for bridge simulation

[fangohr]

$ karabo-bridge-server-sim --help
usage: karabo-bridge-server-sim [-h] [--protocol {1.0,2.1,2.2}]
                                [--detector {AGIPD,LPD}]
                                [--serialisation {msgpack,pickle}]
                                port

Run a Karabo bridge server producing simulated data.

positional arguments:
  port                  TCP port the server will bind

optional arguments:
  -h, --help            show this help message and exit
  --protocol {1.0,2.1,2.2}
  --detector {AGIPD,LPD}
                        Which kind of detector to simulate
  --serialisation {msgpack,pickle}

We need to extend the above output to show which options are chosen by default (i.e. which protocol, which detecter, which serialisation).