Create longest and shortest path criteria

[Bostwickenator]

This adds a feature to prioritize by longest or shortest path. I find this useful for deduplicating large volumes of photo backups where some files are in deep folders direct from an SD card eg card2/DCIM/100MEDIA/ and files inspected and used from this may be in a shorter path like card2/keepers.

Also helps with situations where previous backups have been duplicated inside in later backups. Path length can quickly prefer one set or the other without manually specifying all the folders.

It's included under Filename criterion because it seemed easier to integrate there.

[tflo]

feature to prioritize by longest or shortest path

This is a very good idea. I recently had a use case for just that!

[Bostwickenator]

Anything I need to do on this PR?