CBQE-2240:tuq generator: add groups handling

Change-Id: I2c14b1c04dc45bfc399e59f1ed59ce48f52225ba
Reviewed-on: http://review.couchbase.org/36885
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>