RFR: Allow reading label configuration from a hosted repository file

[Robin Westberg]

Hi all,

Please review this change that allows the PR bot to read (and reread on updates) label configuration from a file
instead of storing it in the configuration.

Best regards,
Robin

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

Commit messages:
 - Allow reading label configuration from a hosted repository file

Changes: https://git.openjdk.java.net/skara/pull/767/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=767&range=00
  Stats: 420 lines in 9 files changed: 241 ins; 127 del; 52 mod
  Patch: https://git.openjdk.java.net/skara/pull/767.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/767/head:pull/767

PR: https://git.openjdk.java.net/skara/pull/767