Switch from events to setting service flags.

Instead of firing events on the topology, we're switching to setting
flags on the service and unit models in the DB. That way the data is
persistent across state changes (i.e., when a user switches from
service view to machine view) and we maintain one single source of
truth.
After reading more of the code I'm thinking that `service` should be {Object|Array} because it will simplify the handlers which call this method.