new options for open cracks


git-svn-id: https://geuz.org/svn/gmsh/trunk@16558 59c8cabf-10d6-4a28-b43f-3936b85956c4
new Recursive Show/Hide/Color


git-svn-id: https://geuz.org/svn/gmsh/trunk@16559 59c8cabf-10d6-4a28-b43f-3936b85956c4