added set_range function, exposed missing property managers and removed redundant code

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1079 fdac6126-5c0c-442c-9429-916003d36597
added a python-specific unit test

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1080 fdac6126-5c0c-442c-9429-916003d36597