RFR: 2170: Warn on trailing period in PR titles

[Zhao Song]

This patch is trying to add a new jcheck called "issuestitle". This jcheck would check if the issue's title has a trailing period. And we would like to configure "issuestitle" jcheck as warning in the repos since in some cases, trailing periods are valid.

When implementing this, I found that although we can configure a jcheck as warning in the jcheck configuration file(.jcheck/conf), we fail to differentiate between jchecks as error and jchecks as warning. When jchecks fail as warnings, they cause the local jcheck to exit with a status code of 1. Also, they will be integration blockers when Skara bots evaluate pull requests.  Therefore, in this patch, I also make Skara CLI and Skara bots be able to handle jcheck warnings properly.

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Commit messages:
 - update
 - add Warnings to pr body
 - SKARA-2170

Changes: https://git.openjdk.org/skara/pull/1638/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1638&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2170
  Stats: 361 lines in 11 files changed: 256 ins; 10 del; 95 mod
  Patch: https://git.openjdk.org/skara/pull/1638.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1638/head:pull/1638

PR: https://git.openjdk.org/skara/pull/1638