Fix of https://github.com/prusa3d/Slic3r/issues/285

Refactored Model.cpp/hpp to C++x11 loops,
simplified the mesh / bbox handling.

xs/xsp/Print.xsp

@@ -64,8 +64,6 @@ _constant()
     Ref<Point3> size()
         %code%{ RETVAL = &THIS->size; %};
     Clone<BoundingBox> bounding_box();
-    Ref<Point> _copies_shift()
-        %code%{ RETVAL = &THIS->_copies_shift; %};
     
     bool typed_slices()
         %code%{ RETVAL = THIS->typed_slices; %};