split FTDecay files; rename -> FFGaussSphere

Core/Aggregate/FTDecay1D.cpp

Core/Aggregate/FTDecay1D.h

Core/Aggregate/FTDecay2D.cpp

Core/Aggregate/FTDecay2D.h

Core/Aggregate/InterferenceFunction1DLattice.cpp

Core/Aggregate/InterferenceFunction2DLattice.h

Core/Basics/Units.h

Core/Detector/IDetector2D.cpp

Core/Detector/RectangularDetector.cpp

Core/Detector/SphericalDetector.cpp

Core/Intensity/SimpleUnitConverters.cpp

Core/Intensity/UnitConverter1D.cpp

Core/Material/MaterialFactoryFuncs.cpp

Core/Multilayer/KzComputation.cpp

Core/Parametrization/INodeVisitor.h

Core/Particle/HomogeneousRegion.cpp

Core/PyIO/PythonFormatting.cpp

Core/SoftParticle/FormFactorGauss.cpp

Core/SoftParticle/FormFactorGauss.h

Core/SoftParticle/FormFactorLorentz.cpp