Allow deduplication of actions in run and finalize phases

I would renemate that file to "deduplication.rb" to better express what it shows (the content itself is not that important). Also, it would be nice to plan to tasks, one with the duplication turned on and the second turned off (through some parameter in `PackageManagement.plan`,  printing the links to the duplicate and deduplicate task into the console, so that one can just click and see the difference