Merge branch 'ff50' into 'develop'

Core/Export/SampleToPython.cpp

Core/Export/SimulationToPython.cpp

Device/Detector/RectangularDetector.cpp

Device/Detector/RectangularDetector.h

Examples/fit61_Galaxi/sample_builder.py

Examples/scatter2d/BiMaterialCylinders.py

Examples/scatter2d/BuriedParticles.py

Examples/scatter2d/HexagonalLatticesWithBasis.py

Examples/scatter2d/Interference2DCenteredSquareLattice.py

Examples/scatter2d/MagneticSpheres.py

Examples/scatter2d/ParticlesCrossingInterface.py

Examples/scatter2d/PolarizedSANS.py

...s/scatter2d/disabled/Interference2DLatticeSumOfRotated.py

GUI/Model/From/GUIDomainSampleVisitor.cpp

GUI/Model/Group/DistributionItems.cpp

GUI/Model/Instrument/RectangularDetectorItem.cpp

GUI/Model/Sample/ItemWithParticles.cpp

GUI/Model/Session/SessionModel.cpp

GUI/Model/Session/SessionXML.cpp

GUI/View/Fit/SliderSettingsWidget.cpp