All SessionItems switched to new addGroupProperty method

GUI/coregui/Models/BeamItem.cpp

GUI/coregui/Models/GroupPropertyRegistry.cpp

GUI/coregui/Models/GroupPropertyRegistry.h

GUI/coregui/Models/IntensityDataItem.cpp

GUI/coregui/Models/MaterialItem.cpp

GUI/coregui/Models/ParticleCompositionItem.cpp

GUI/coregui/Models/ParticleCoreShellItem.cpp

GUI/coregui/Models/ParticleItem.cpp

GUI/coregui/Models/RectangularDetectorItem.cpp

GUI/coregui/Models/SessionItem.cpp

GUI/coregui/Models/SessionItem.h

GUI/coregui/Models/SphericalDetectorItem.cpp

GUI/coregui/Views/InstrumentWidgets/DetectorMaskDelegate.cpp