added missing base class for property handles

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1066 fdac6126-5c0c-442c-9429-916003d36597
exposed additional mesh functions

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1067 fdac6126-5c0c-442c-9429-916003d36597
added a unit test for properties

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1068 fdac6126-5c0c-442c-9429-916003d36597