pythonPackages: add pyrax

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixpkgs: add COPRTHR 1.6

COPRTHR is a very excellent little SDK implementing OpenCL and related
tech for regular multicore processors, as well as things like my new
Parallella (along with remote/networked OpenCL compute support).

Signed-off-by: Austin Seipp <aseipp@pobox.com>