Refactorize, putting passes stuff in separate module.

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>
Fix backward compatibility issue with numpy.

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>
Add export method to graph

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>
Sort passes to avoid conflicts.

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>
Bump up version number.

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>