Spherical and Rectangular detector items now derived from common base DetectorItem.

GUI/coregui/Models/DetectorItems.h

GUI/coregui/Models/ItemFactory.cpp

GUI/coregui/Models/RectangularDetectorItem.cpp

GUI/coregui/Models/RectangularDetectorItem.h

GUI/coregui/Models/SphericalDetectorItem.cpp

GUI/coregui/Models/SphericalDetectorItem.h

GUI/coregui/Models/TransformFromDomain.cpp

GUI/coregui/Models/TransformToDomain.cpp

GUI/coregui/Views/ImportDataWidgets/ImportDataAssistant.cpp

GUI/coregui/Views/InstrumentWidgets/DetectorEditorWidget.cpp

GUI/coregui/Views/InstrumentWidgets/DetectorMaskDelegate.cpp

...gui/Views/InstrumentWidgets/RectangularDetectorWidget.cpp

...regui/Views/InstrumentWidgets/SphericalDetectorWidget.cpp

Tests/UnitTests/GUI/TestMapperCases.h