WIP: asynchronous command bus, #199

This merge request contains the requiered configuration (messenger and docker-compose) to use rabbimq for async command and event handling. The TestData2Command was a preliminary version of the new TestDataCommand for #200 (closed).

I'm not sure if the waiting is really needed, if the retries are configured correctly. And the refresh-flag for retrieving read models is also something that doesn't make me happy.