[i427a] GUI: remember the UI state (Closes #427)

GUI/Model/Data/RealItem.cpp

GUI/Model/Data/RealItem.h

GUI/Model/Device/InstrumentModel.h

GUI/Model/Job/JobItem.cpp

GUI/Model/Job/JobItem.h

GUI/Model/Model/JobModel.cpp

GUI/Model/Model/JobModel.h

GUI/Model/Model/RealModel.cpp

GUI/Model/Model/RealModel.h

GUI/Model/Sample/SampleModel.h

GUI/Support/Data/SimulationOptionsItem.cpp

GUI/Support/Data/SimulationOptionsItem.h

GUI/View/Fit/ParameterTuningDelegate.cpp

GUI/View/Fit/ParameterTuningDelegate.h

GUI/View/Fit/ParameterTuningWidget.cpp

GUI/View/Fit/ParameterTuningWidget.h

GUI/View/Fit/SliderSettingsWidget.cpp

GUI/View/Fit/SliderSettingsWidget.h

GUI/View/Import/RealDataPresenter.cpp

GUI/View/Import/RealDataPresenter.h