MB-12179: Make the scan API's accessable through the KVStore

Change-Id: Iec845dd48b5f753ddee13793c8c2973196a1eb0a
Reviewed-on: http://review.couchbase.org/41827
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>