JCBC-76: Replica Read Command

This changeset implements the replica read command
on both the application level facing CouchbaseClient
and also implements the backend changes neeeded.

It depends on the corresponding changes on the SPY
project (see SPY-113).

Change-Id: Idfd0836adfd5212152f369e8e624d45c4c9ca2b4
Reviewed-on: http://review.couchbase.org/24750
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>