Removed some more obsolete methods related to unit conversion

Core/Fitting/FitObject.cpp

Core/Fitting/FitObject.h

Core/Fitting/FitSuiteObjects.cpp

Core/Fitting/FitSuiteObjects.h

Core/Instrument/DetectorFunctions.cpp

Core/Instrument/DetectorFunctions.h

Tests/UnitTests/Core/Detector/SphericalDetectorTest.h

auto/Wrap/doxygen_core.i

auto/Wrap/doxygen_fit.i

auto/Wrap/libBornAgainCore.py

auto/Wrap/libBornAgainCore_wrap.cpp

auto/Wrap/libBornAgainFit.py

auto/Wrap/libBornAgainFit_wrap.cpp