exposed mesh items

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1062 fdac6126-5c0c-442c-9429-916003d36597
exposed additional mesh functions (low-level adding new items & more)

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1063 fdac6126-5c0c-442c-9429-916003d36597