CBPS-206: Add a new field "topics" to ReverseLookupDocument
CBPS-206: Add a new field "topics" to ReverseLookupDocument

This new field replaces the existing field "partition_id" which is
not currently used.

Topics is an array of keys. It can be used for JOIN queries.

Change-Id: I99e9a3a933eabbcc63942cbc996b24c58a0fcac4
Reviewed-on: http://review.couchbase.org/68900
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

couchbase/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner