Summary: If you import a repository you may trigger a large number of irrelevant audits. Provide a tool to nuke them.
Test Plan: Ran "audit.php Q" (does not exist), "audit.php P" (phabricator) from various repository states.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran, epriestley
Maniphest Tasks: T904, T940
Differential Revision: https://secure.phabricator.com/D1791
