[field] consolidate Datafield related code ()

CHANGELOG

Device/Data/ArrayUtil.cpp

Device/Data/ArrayUtil.h

Device/Data/DataUtil.cpp

Device/Data/DataUtil.h

Device/IO/ReadRefsans.cpp

Device/IO/ReadWrite2DTable.cpp

Device/IO/ReadWriteINT.cpp

GUI/Model/Device/RealItem.cpp

GUI/View/Plot2D/IntensityDataFFTPresenter.cpp

Sim/Fitting/FitObjective.cpp

Sim/Fitting/FitObjective.h

Tests/Unit/Device/ArrayUtilsTest.cpp

Tests/Unit/Device/IntensityDataFunctionsTest.cpp

Tests/Unit/GUI/TestDataItems.cpp

Wrap/Swig/libBornAgainSim.i

auto/Wrap/libBornAgainDevice.py

auto/Wrap/libBornAgainDevice_wrap.cpp

auto/Wrap/libBornAgainSim.py

auto/Wrap/libBornAgainSim_wrap.cpp