cBQE-2240;: tuq generator: add groups handling

Change-Id: I0cd66692bcfe1ce54e22cfcbbf13e0e11aa91948
Reviewed-on: http://review.couchbase.org/36970
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>