RFR: 2170: Warn on trailing period in PR titles [v4]

[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 or leading lowercase letter. And we would like to configure "issuestitle" jcheck as warning in the repos since in some cases, trailing periods or leading lowercase letter 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.

Zhao Song has updated the pull request incrementally with one additional commit since the last revision:

  review comment

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1638/files
  - new: https://git.openjdk.org/skara/pull/1638/files/584bcbfe..b02f549e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1638&range=03
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1638&range=02-03

  Stats: 72 lines in 5 files changed: 16 ins; 3 del; 53 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