Get the Controller to catch changes to the Configuration

[diconico07]

With the refactor of the Agent, its behavior changed so that it doesn't delete Instances whenever a change to the Configuration happen, this led to the Controller no longer doing anything when a change happens that only impacts the way the Controller do its job.

To solve this, the Controller should watch for changes to the Configuration and trigger updates when relevant.

Going back to the old behavior of the agent is not wanted as this overall change was meant in preparation of the split of the Configuration into two resources.