Improved accuracy of ModelVolume matrix store / restore

into the 3MF / AMF.
Improved accuracy of ModelVolume's mesh transform back from Object's
coordinate space to its own coordinate space after reloading
from 3MF / AMF.

src/libslic3r/Model.hpp

@@ -466,6 +466,7 @@ public:
 
     const Geometry::Transformation& get_transformation() const { return m_transformation; }
     void set_transformation(const Geometry::Transformation& transformation) { m_transformation = transformation; }
+    void set_transformation(const Transform3d &trafo) { m_transformation.set_from_transform(trafo); }
 
     const Vec3d& get_offset() const { return m_transformation.get_offset(); }
     double get_offset(Axis axis) const { return m_transformation.get_offset(axis); }