Implement a sensible "service turndown" workflow

Right now there's no "clean" way to turn down a service, if removed from services.yml many artifacts (including running containers) will be left over and not cleaned up by float, because float doesn't touch things it does not "own".

A possible solution from the user's perspective could be: set enabled=false on the service metadata, and do a push to remove all associated artifacts. To implement this, we're going to need to modify the float.py plugin to not filter out 'enabled=false' services but to instead keep including them without any hosts assignment.