Rebind location: avoid “id” being added to config

- which was breaking JcloudsLocation.createTemporarySshMachineLocation
Adds expungeMembers to DynamicCluster’s QuarantineGroup
squash with “Adds isRebinding”
AttributePollHandler: Reduce logging of recurring error
Rebind: simplify LookupContext

- Previously we needed to pass the expected type; now we construct
  a “memento manifest” that tells us the ids and types of entity,
  location, etc.
- Code was logging lots of incorrect warnings such as:
  “Entity with id MGc3cuT8 does not match type class io.cloudsoft.Foo”
Persist on policy-reconfigured
Persistence: expunge policy when removed from entity