Support CSV input option, which also allows tests to work again

- CSV input doesn't have to be exactly like `sacct` would be, so that
  test data doesn't have to be updated for every schema change.

- --csv-input allows CSV to be fed in.

- Adjust different other parsers so that they can accept missing input
  fields (mainly the JobID fields), since with CSV various fields may
  be missing.  This may change outputs, mainly giving nulls in places
  where there may have been empty strings before.