Move Error class from utils/GUIHelpers to Models/Error

GUI/Models/ComboProperty.cpp

GUI/Models/Data1DViewItem.cpp

GUI/Models/DataItem.cpp

GUI/Models/DataItemUtils.cpp

GUI/Models/DataProperties.cpp

GUI/Models/DataPropertyContainer.cpp

GUI/Models/DomainObjectBuilder.cpp

GUI/Models/DomainSimulationBuilder.cpp

GUI/Models/Error.cpp

GUI/Models/Error.h

GUI/Models/FitParameterItems.cpp

GUI/Models/FitParameterProxyModel.cpp

GUI/Models/GUIDomainSampleVisitor.cpp

GUI/Models/GUIObjectBuilder.cpp

GUI/Models/GroupInfo.cpp

GUI/Models/GroupInfoCatalog.cpp

GUI/Models/GroupItem.cpp

GUI/Models/InstrumentItems.cpp

GUI/Models/IntensityDataItem.cpp

GUI/Models/ItemCatalog.cpp