AthenaServices+AthenaPoolExampleAlgorithms: Use ThinningCache for variable selection.

AthenaOutputStream processes ItemList information, including requests for dynamic variable information. To prevent different streams from interfering with each other, we want to put this information in the ThinningCache, rather than in the EDM objects themselves.

Changed AthenaOutputStream so that rather than calling selectAux, it records variable selection information in the event store. This is then read by ThinningCacheTool, to make the information available in the ThinningCache

Updated reference files in AthenaPoolExampleAlgorithms.