- Update NullJob to subclass Job
- Remove unnecessary size pre-read in _getMatches() as file sizes are
already loaded during file scan via stat call
- Skip ref check if contents scan as the scan already prevents this from
happening, some of the other scans do things differently and need to
be reviewed before removing this post step completely
- Add guard on partial hashing to just hash the whole file if smaller
than the offset and size and use the value for both the partial digest
and digest