new feature: tmp bare repo: show position for DM|FM if SHA1

[lomnido]

this allows to display position (before or after) for Deep Manifest or Future Manifest

Also fix:

• COMMON PATH calculation for 'dump-manifest' command
• '--show-leftovers-status' allow to display leftover status (if available)
• calculation of COMMON PATH (sometimes it does not shorten the Path as it should)

For 'dump-manifest':

• '--skip-manifest': excludes Manifest Repo (DM) if found
• '--only-manifest': only consider Manifest Repo (DM) if found
• '--sha1-only' put SHA1 record to Manifest for each Repo (--skip-manifest and --only-manifest are respected)