RFR: 411: Warn when a PR issue is not of a primary type

[Erik Helin]

Hi all,

please review this patch that makes it possible the issue types that should be allowed to be referenced from a PR for a
repository.

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

Thanks,
Erik

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Commit messages:
 - 411: Warn when a PR issue is not of a primary type

Changes: https://git.openjdk.java.net/skara/pull/665/files
 Webrev: https://webrevs.openjdk.java.net/skara/665/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-411
  Stats: 146 lines in 5 files changed: 134 ins; 3 del; 9 mod
  Patch: https://git.openjdk.java.net/skara/pull/665.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/665/head:pull/665

PR: https://git.openjdk.java.net/skara/pull/665