RFR: Add support for Issue links with Jira implementation

[Robin Westberg]

Hi all,

Please review this change that adds support for adding links to an issue, with an implementation for Jira and TestIssue.

Best regards,
Robin

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Commits:
 - a10e4a3b: Add support for Issue links with Jira implementation

Changes: https://git.openjdk.java.net/skara/pull/306/files
 Webrev: https://webrevs.openjdk.java.net/skara/306/webrev.00
  Stats: 387 lines in 10 files changed: 384 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/306.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/306/head:pull/306

PR: https://git.openjdk.java.net/skara/pull/306