Merge branch 'refactor_model' into 'develop'

GUI/Models/FitParameterHelper.cpp

GUI/Models/FitParameterItems.cpp

GUI/Models/FitParameterItems.h

GUI/Models/FitParameterProxyModel.cpp

GUI/Models/FitParameterProxyModel.h

GUI/Models/FitSuiteItem.cpp

GUI/Models/FitSuiteItem.h

GUI/Models/ItemCatalog.cpp

GUI/Models/JobItem.cpp

GUI/Models/JobModelFunctions.cpp

GUI/Models/SessionItem.h

GUI/Views/FitWidgets/FitFlowWidget.cpp

GUI/Views/FitWidgets/FitParameterWidget.cpp

GUI/Views/FitWidgets/FitSessionController.cpp

GUI/Views/FitWidgets/RunFitControlWidget.cpp

GUI/Views/FitWidgets/RunFitControlWidget.h

GUI/Views/MaskWidgets/MaskViewFactory.cpp

Tests/UnitTests/GUI/TestFitParameterModel.cpp