- Define profiles that group services that share a specific context, and 
  in this way allow these services to be started more easily.
- Assign the default network a name that can be referenced in other
  Docker Compose files. This makes the IoT Broker network easier to
  share with and use by other projects (e.g. device integration
  projects).
- While here, add a section on how to run the IoT Broker locally (using
  the newly added profiles) to the documentation.

Approved-by: David Thiesen <david.thiesen@iml.fraunhofer.de>
Merged-by: David Thiesen <david.thiesen@iml.fraunhofer.de>