! Added --liberal, which changes the way prune works to identify more duplication.
Refactored extracting update_masses.
Refactored extracting prune_conservatively.
Added prune_liberally and run it optionally in prune.
+ Made report's sort more stable, so I can do better comparison runs.
Added Array#delete_eql for liberal prune.

[git-p4: depot-paths = "//src/flay/dev/": change = 8323]