Add suport for NodesExt to BucketConfig

Change-Id: I5053ccfb2a54486ea4ff963e39da0e2807f06955
Reviewed-on: http://review.couchbase.org/40157
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>