- fix up de_score so that it actually reflects what we could save by
  deduping.
- make a bunch of printing in print_results verbose-only. By default it only
  shows the total savings posible now.
- use print_results in dedupe_results so that the user gets a nice display
  of what might be saved
- add a print at the end of dedupe results showing how much was actually
  saved.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
- allow opening files readonly by -A option. This works well with readonly
  snapshots.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>