R1:d2fbfaa4e8f5

Allow configuring fresh and stale revision age

Summary: People will want to configure/disable this.

Test Plan: Displayed Action Required, changed numbers to 0/0, 1/0, 0/30.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3353