Codegen PartitionedAggregationNode

Change-Id: Iea1f32aa404689cd310a9822f5bb437b1aeda9bd
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4148
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 0436cc98f9c22204a6ed3f4f0d65757dff00539e)
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4213
Tested-by: Skye Wanderman-Milne <skye@cloudera.com>