Support disabled, aborted, and never run jobs

In addition to cleanly supporting these other job types, this pull request also updates the stats rollup to only display fields that have a non-zero value.

This is based on GH-36.
There are still a handful of job states, like "unstable", that we don't handle - I want to make sure the numbers actually add up. In normal operation it won't be shown, but it will be present if needed.