Add -min-duration selection to `jobs`

[lars-t-hansen]

We can print "everything" and filter but for some queries it will be more sensible to filter by duration before further processing. It's an oversight in the filtering that we can't filter by duration. -min-duration could take either a number of seconds or the usual WwDdHhMm spec.

[lars-t-hansen]

This is bogus. The -min-runtime switch filters by duration.