ENCH: Adding export to STL (STereoLithography) file format

git-svn-id: http://svn.3dbar.org/svn/3dbar_sharable/trunk@213 bf95b417-27cd-4b1f-9e77-6486572a7b41
format description made uniform

git-svn-id: http://svn.3dbar.org/svn/3dbar_sharable/trunk@214 bf95b417-27cd-4b1f-9e77-6486572a7b41