While creating hard links, check if they're already linked first.
This saves SUBSTANTIAL time in Time Machine directories where many
files are already hard links.
Also, be clearer when running about what exactly it is we're doing
with each file.
This initial commit includes a directory deduplicator (for thinning out
Time Machine snapshots) and an automatic tool to detect and apply the
necessary metadata for a successful tmutil inherit (needed when you
want to use a backup drive with a new computer, for example).
