rename GUI/Model/Sample/MaterialItem -> GUI/Model/Material/

GUI/Model/FromCore/ItemizeSample.cpp

GUI/Model/Job/ParameterTreeBuilder.cpp

GUI/Model/Material/MaterialItem.cpp

GUI/Model/Material/MaterialItem.h

GUI/Model/Project/ProjectDocument.cpp

GUI/Model/Sample/ItemWithMaterial.cpp

GUI/Model/Sample/MaterialModel.cpp

GUI/Model/Sample/ParticleItem.cpp

GUI/Model/ToCore/SampleToCore.cpp

GUI/View/Material/MaterialEditorDialog.cpp

GUI/View/Material/MaterialTableModel.cpp

GUI/View/Realspace/RealspaceWidget.cpp

GUI/View/Sample/LayerForm.cpp

GUI/View/Sample/MaterialInplaceForm.cpp

Tests/Unit/GUI/TestMaterialItems.cpp