Allow saving lint errors to database
Summary: This saves lint errors to the path change of current commit. It requires pushed revision. It doesn't save difference from previous commit mentioned in T2038#comment-4 - I don't plan doing it after all, everything would be much more complicated and the amount of data saved with this approach isn't that bad.
Test Plan: Applied patch, ran script, verified DB.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2038
Differential Revision: https://secure.phabricator.com/D3899