CLI version sort

Changing the way the sort parameter of a criteria is stored to be by unit instead of association. This isn't ideal either since it precludes sorting by date added to the repo, but I suspect the more common case is to search by unit fields instead.

We need a few things in this area. Another big one is that --gt assumes integers but we need a way to have it work on strings as well. I may circle back on that one by the end of the sprint but for now I'm leaving this at the sort change.