RFR: 420: Expand JBS issues in PR titles

[Erik Helin]

Hi all,

please review this small patch that automatically expands issue ids in pull request titles to the "id: title" format.
For example if a pull request for the [skara](https://github.com/openjdk/skara) repository has the title `420`, then
the pull request title will be automatically set to `420: Expand JBS issues in PR titles`. I have been fairly
conservative in what we expand, we only expand titles exactly matching `PROJECT-ID` or `ID`, i.e. `SKARA-420` or `420`.

Testing:
- [x] Added two new unit tests
- [x] `make test` passes on Linux x64

Thanks,
Erik

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Commit messages:
 - 420: Expand JBS issues in PR titles

Changes: https://git.openjdk.java.net/skara/pull/672/files
 Webrev: https://webrevs.openjdk.java.net/skara/672/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-420
  Stats: 105 lines in 2 files changed: 104 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/672.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/672/head:pull/672

PR: https://git.openjdk.java.net/skara/pull/672