New doxygen group for input/output classes.

Core/InputOutput/IntensityDataIOFactory.cpp

Core/InputOutput/IntensityDataIOFactory.h

Core/InputOutput/OutputDataReadFactory.h

Core/InputOutput/OutputDataReadStrategy.h

Core/InputOutput/OutputDataReader.h

Core/InputOutput/OutputDataWriteFactory.h

Core/InputOutput/OutputDataWriteStrategy.h

Core/InputOutput/OutputDataWriter.h

Core/InputOutput/TiffHandler.h

Core/PythonAPI/src/IntensityDataIOFactory.pypp.cpp

Doc/Doxygen/defgroups.doc

Doc/Doxygen/userapi.doc

Examples/python/utils/plot_intensity_data_diff.py

dev-tools/python-bindings/settings_core.py