[Rev 04] RFR: 223: Make required re-reviewing configurable

[Robin Westberg]

> Hi all,
> 
> Please review this change that makes it possible to configure (per project) if additional commits to a pull request renders previous reviews invalid or not. It also tweaks the behavior of the `rfr` label slightly - instead of dropping it when a PR is reviewed and receives the `ready` label, is will remain for as long the PR is eligible for further reviews. This should reduce the number of label transitions when this feature is enabled.
> 
> The change also contains a bit of refactoring to make it easier to add more project specific configuration in the future.
> 
> Best regards,
> Robin

The pull request has been updated with 1 additional commit.

-------------

Added commits:
 - 2f9a133f: Fix test issues

Changes:
  - all: https://git.openjdk.java.net/skara/pull/376/files
  - new: https://git.openjdk.java.net/skara/pull/376/files/ac9729f3..2f9a133f

Webrevs:
 - full: https://webrevs.openjdk.java.net/skara/376/webrev.04
 - incr: https://webrevs.openjdk.java.net/skara/376/webrev.03-04

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/376.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/376/head:pull/376

PR: https://git.openjdk.java.net/skara/pull/376