Implemented computing the GDF GroupBy solution and comparing it to the reference solution. Verified working on all aggregators expect AVG.
Implemented computing the GDF GroupBy solution and comparing it to the reference solution. Verified working on all aggregators expect AVG.

gpuopenanalytics/libgdf,gpuopenanalytics/libgdf,gpuopenanalytics/libgdf,gpuopenanalytics/libgdf