openscad: bump to 2013.01

Bump to latest release. Use tarball instead of git.
openscad: add longDescription and license

longDescription is taken from openscad homepage.
openscad: compile the correct version number

The default version info that is compiled into openscad is the build
date(!). Force the version to the actual release version instead.
Merge pull request #489 from bjornfor/openscad

openscad: version bump + small fixes