Complete IBucket implementation for Memcached and Couchbase Buckets

Change-Id: If6fb47b9e4a5201e625f155dadf45696b8666674
Reviewed-on: http://review.couchbase.org/40507
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>