temporarily split Intensity, Instrument, Detector into many subdirs

Core/Data/LLData.cpp

Core/Data/LLData.h

Core/Data/OutputData.cpp

Core/Data/OutputData.h

Core/Data/OutputDataIterator.h

Core/Detector/IntensityDataFunctions.cpp

Core/Detector/IntensityDataFunctions.h

Core/Detector/RectangularPixel.cpp

Core/Detector/RegionOfInterest.cpp

Core/Detector/SimulationArea.cpp

Core/Detector/SimulationAreaIterator.cpp

Core/Export/SimulationToPython.cpp

Core/Fitting/FitObjective.h

Core/Fitting/ObjectiveMetric.cpp

Core/Fitting/SimDataPair.cpp

Core/Histo/Histogram1D.cpp

Core/Histo/Histogram1D.h

Core/Histo/Histogram2D.cpp

Core/Histo/Histogram2D.h

Core/Histo/IHistogram.cpp