1 Allow the output of a job to be listed. This is pretty easy since we
2 know the tmpdir and the output file.
4 For Whentools.once and Whentools.max:
6 - Add a ~group parameter so we can run no more than "n" jobs in one
9 - Add a ~kill_oldest (bool) parameter so we can kill the oldest jobs
10 and start the new job.
12 Implement native dynlink.