IDetector2D classes now decide on default axis names

Core/Algorithms/inc/GISASSimulation.h

Core/Algorithms/inc/IDetector2D.h

Core/Algorithms/inc/Instrument.h

Core/Algorithms/inc/RectangularDetector.h

Core/Algorithms/inc/SphericalDetector.h

Core/Algorithms/src/GISASSimulation.cpp

Core/Algorithms/src/IDetector2D.cpp

Core/Algorithms/src/Instrument.cpp

Core/Algorithms/src/RectangularDetector.cpp

Core/Algorithms/src/SphericalDetector.cpp

Core/PythonAPI/src/GISASSimulation.pypp.cpp

Core/PythonAPI/src/IDetector2D.pypp.cpp

Core/PythonAPI/src/Instrument.pypp.cpp

Core/Tools/inc/BornAgainNamespace.h