WIP: egamma ART change from master to rel21
Port changes made to egamma ART master branch to rel 21: relates to additonal histograms (photon ID !42097 (merged)) and to python code cleaning (!42526 (merged))
Port changes made to egamma ART master branch to rel 21: relates to additonal histograms (photon ID !42097 (merged)) and to python code cleaning (!42526 (merged))