Some OpenJDK projects have a rule or recommendation that a PR should be out for review for 24 hours (not counting weekends). It would be useful to be able to configure a minimum time on a per-repo basis (either in .jcheck/conf or in Skara's repo config).

The minimum time should be computed using the time the PR was most recently made "rfr" as the start time.

Some things to consider:

* Should this be a warning or an integration blocker (or maybe both, with the selection being another config parameter)?
* If this is a blocker, who can override when there is an urgent need (e.g., a P1 build failure or a backout of a fix that broke Tier2 tests)? Any Reviewer? Any 2 Reviewers?
* Should this account for weekends and holidays? If holidays, which ones?