RFR: Bridgekeeper bot

[Robin Westberg]

Hi all,

Please review this change that implements a "Bridgekeeper" bot. It can be enabled for mirror repositories that do not currently accept pull requests.

Best regards,
Robin

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

Commits:
 - 869b7a98: Initial implementation

Changes: https://git.openjdk.java.net/skara/pull/245/files
 Webrev: https://webrevs.openjdk.java.net/skara/245/webrev.00
  Stats: 338 lines in 6 files changed: 338 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/245.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/245/head:pull/245

PR: https://git.openjdk.java.net/skara/pull/245