Rudder

We need to persist compliance in base to be able to:

- restore the last known state when rudder start up
- more finely control persistance expiration by node.

More saillantly, we want to be able to address the case:
- a node compliance should be kept for several days when a node is not answering (typically: laptop when people go on hollidays),
- we want to avoid keeping run reports for more than a day for storage reason

That case is not possible without persistence in base.
Today, we compute compliance from expected reports and last run reports, always. If we don't have run reports, we don't have compliance.