Serialize PermutationTree: can access byte stream from interface

git-svn-id: https://geuz.org/svn/gmsh/trunk@16601 59c8cabf-10d6-4a28-b43f-3936b85956c4
widgetLabelRatio = 0.45


git-svn-id: https://geuz.org/svn/gmsh/trunk@16602 59c8cabf-10d6-4a28-b43f-3936b85956c4