Doxygen comments and other copy editing here and there

Core/InputOutput/OutputDataWriteStrategy.h

Core/InputOutput/OutputDataWriter.cpp

Core/InputOutput/OutputDataWriter.h

Core/Instrument/Beam.cpp

Core/Instrument/Beam.h

Core/Instrument/DetectorMask.cpp

Core/Instrument/DetectorMask.h

Core/Instrument/Histogram2D.cpp

Core/Instrument/Histogram2D.h

Core/Instrument/IHistogram.h

Core/Instrument/IIntensityNormalizer.h

Core/Instrument/OutputData.h

Core/Simulation/GISASSimulation.cpp

Core/Simulation/GISASSimulation.h

Core/Simulation/OffSpecSimulation.h