EC_GraphicsViewCanvas: Workaround in case the EC is added on a mesh with empty material refs, or in case existing material refs cannot be loaded. Also removed duplicated code.
Undo manager: Do a proper clean up when destroying UndoManager
build-mac-deps: s/-03/-O3/
build-mac-deps: Add option to make Xcode project, instead of Makefiles
Move TransformAttributeWeakPtr to IAttribute.h
Add undo / redo actions for transform gizmo manipulations. Closes #634