rename -> Span::low(), hig()

Base/Types/Span.cpp

Base/Types/Span.h

Resample/Particle/ReParticle.cpp

Resample/Processed/ReSample.cpp

Resample/Processed/Slicer.cpp

Resample/Slice/ProfileHelper.cpp

Resample/Slice/Slice.cpp

Resample/Slice/Slice.h

Resample/Slice/SliceStack.cpp

Resample/Slice/ZLimits.cpp

Resample/Slice/ZLimits.h

Sample/Multilayer/MultiLayer.cpp

Sample/Multilayer/MultiLayer.h

auto/Wrap/libBornAgainSample.py

auto/Wrap/libBornAgainSample_wrap.cpp