exposed garbage collection that keeps track of handles

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1121 fdac6126-5c0c-442c-9429-916003d36597
added a garbage collection unit test

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1122 fdac6126-5c0c-442c-9429-916003d36597
exposed io functions

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1123 fdac6126-5c0c-442c-9429-916003d36597
added five io unit tests

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1124 fdac6126-5c0c-442c-9429-916003d36597