RFR: 439: Improve command filtering when bridging mails

[Robin Westberg]

Hi all,

Please review this change that improves the command comment filtering done by the mailinglist bridge bot, to match more
closely what the pull request bot would consider as commands.

Best regards,
Robin

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Commit messages:
 - Improve the command comment filtering

Changes: https://git.openjdk.java.net/skara/pull/756/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=756&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-439
  Stats: 23 lines in 3 files changed: 14 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/skara/pull/756.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/756/head:pull/756

PR: https://git.openjdk.java.net/skara/pull/756