remove topic

as a comment in the code already mention, we could entirely remove the --topic, because each action class already is bind to a topic. For example its redundant to use the run-create-thing-on-minio-action-service and also subscribe to the topic thing_created because we can hardcode this into the class.

Some questions that arise:

• Do we loose flexibility?
• Do we intent to make different classes that listen to the same topic?

any thoughts?