Diver - Extract more contributors from Git commits

[pylapp]

Today the extract-contributors-lists.rb ruby scripts only extract authors of commits.

However contributors or people involved in the scanned project can also appear in other fields of a commit, e.g.:

• From:
• Committer:
• Signed-off:
• Co-developed-by:
• Co-authored-by:
• Acked-by:
• Reviewed-by:

This scanner should be improved.

See for example this publication.