Merge branch 'EventFormatMetaData' into 'master'

...naPoolMultiTest/share/AthenaPoolMultiTestEventNoSplit.ref

...henaPoolMultiTest/share/AthenaPoolMultiTestEventSplit.ref

...MultiTest/share/AthenaPoolMultiTestEventSplitDecision.ref

...thenaPoolMultiTest/share/AthenaPoolMultiTestPropagate.ref

...tabaseTest/AthenaPoolMultiTest/share/SplittableData_jo.py

Control/AthenaKernel/AthenaKernel/IMetaDataSvc.h

Control/AthenaServices/share/AthenaOutputStream_test.ref

Control/AthenaServices/src/MetaDataSvc.cxx

Control/AthenaServices/src/MetaDataSvc.h

...ol/DataModelTest/DataModelRunTests/share/xAODTestRead.ref

...DataModelTest/DataModelRunTests/share/xAODTestRead2_jo.py

...odelTest/DataModelRunTests/share/xAODTestReadFilter_jo.py

...ModelTest/DataModelRunTests/share/xAODTestReadThinned.ref

.../DataModelTest/DataModelRunTests/share/xAODTestRead_jo.py

...elTest/DataModelRunTests/share/xAODTestTypelessRead_jo.py

...elTest/DataModelRunTests/share/xAODTestWriteThinned_jo.py

...DataModelTest/DataModelRunTests/share/xAODTestWrite_jo.py

Control/xAODRootAccess/Root/TEvent.cxx

Control/xAODRootAccess/Root/Utils.cxx

Control/xAODRootAccess/xAODRootAccess/tools/Utils.h