refactor to avoid usage of global access to material model (OOD)

GUI/Model/Material/MaterialModel.cpp

GUI/Model/Material/MaterialModel.h

GUI/Model/Sample/ItemWithMaterial.cpp

GUI/View/SampleDesigner/LayerOrientedSampleEditor.cpp

GUI/View/SampleDesigner/LayerOrientedSampleEditor.h

GUI/View/SampleDesigner/SampleEditorController.cpp

GUI/View/SampleDesigner/SampleEditorController.h

GUI/View/SampleDesigner/SampleView.cpp

Tests/Unit/GUI/TestLayerItems.cpp

Tests/Unit/GUI/TestMaterialModel.cpp

Tests/Unit/GUI/TestRealSpaceBuilderUtils.cpp