Feature: policy persistence (DO NOT MERGED)

@grkvlt - as discussed, can you begin reviewing this. I'm continuing to work on:

1. feature-enablement for persisting policies + enrichers
2. fix ControlledDynamicWebAppCluster's setting of members on rebind
3. nginx losing its members for some reason
4. check that enrichers + policies are cleaned up from persisted state when entity is unmanaged