Add sorting by contribution stats field

[tomice]

The parent project is adding the ability to fine tune the sorting stats. More information can be found here: git-quick-stats/git-quick-stats#189

As well as the parent ticket, here: git-quick-stats/git-quick-stats#134

This will be a fairly heavy ticket touching multiple components of the system, so some care will need to be taken to make sure the tests don't break.