Fixed material writer using wrong stream (Thanks to  Vladimir Chalupecky for the fix). closes #2037

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@999 fdac6126-5c0c-442c-9429-916003d36597
Added simple VTK writer writing only vertices and faces (Thanks to Vladimir Chalupecky for the code). closes #2039

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1000 fdac6126-5c0c-442c-9429-916003d36597
Removed unused variable

git-svn-id: http://openmesh.org/svnrepo/OpenMesh@1001 fdac6126-5c0c-442c-9429-916003d36597