Fix several regressions:

+ improve PropertyMaterialList::readString
+ fix transparency handling in ViewProviderPartExt
+ do not register the private member '_diffuseColor' as property because it would be exposed to the
  public where it can be modified
+ fix ViewProviderPartExt::finishRestoring() to correctly restore old project files
+ fix ViewProviderPartExt::setHighlightedFaces() to correctly show face colours if VBO is enabled
+ fix ViewProviderBoolean::updateData()
  fix ViewProviderMultiFuse::updateData()
  fix ViewProviderMultiCommon::updateData()
  fix ViewProviderCompound::updateData()
  fix ViewProviderFillet::updateData()
  fix ViewProviderChamfer::updateData()
  that all set invalid transparency values
+ Filter ShapeAppearance in ViewProviderBody::unifyVisualProperty
  because body features usually have different number of faces than the body itself
+ manually fix some bad looking auto-formatted code
+ clean up code and remove duplicated code

src/Mod/Part/Gui/ViewProviderCompound.cpp

@@ -111,14 +111,14 @@ void ViewProviderCompound::updateData(const App::Property* prop)
 
             auto vpBase = dynamic_cast<PartGui::ViewProviderPart*>(Gui::Application::Instance->getViewProvider(objBase));
             if (vpBase) {
-                vpBase->ShapeAppearance.setTransparency(vpBase->Transparency.getValue());
-                if (static_cast<int>(vpBase->ShapeAppearance.getSize()) == baseMap.Extent()) {
-                    applyMaterial(hist[index], vpBase->ShapeAppearance, compCol);
+                std::vector<App::Material> baseCol = vpBase->ShapeAppearance.getValues();
+                applyTransparency(vpBase->Transparency.getValue(), baseCol);
+                if (static_cast<int>(baseCol.size()) == baseMap.Extent()) {
+                    applyMaterial(hist[index], baseCol, compCol);
                 }
-                else if (vpBase->ShapeAppearance.getSize() > 0
-                         && vpBase->ShapeAppearance[0] != this->ShapeAppearance[0]) {
-                    vpBase->ShapeAppearance.setSize(baseMap.Extent(), vpBase->ShapeAppearance[0]);
-                    applyMaterial(hist[index], vpBase->ShapeAppearance, compCol);
+                else if (!baseCol.empty() && baseCol[0] != this->ShapeAppearance[0]) {
+                    baseCol.resize(baseMap.Extent(), baseCol[0]);
+                    applyMaterial(hist[index], baseCol, compCol);
                 }
             }
         }