Show all issue, commit and PR comments related to a JIRA issue in one discussion stream

Splitting out this specific request from STASH-2754...

"In general, a pull request will probably be related to some particular issue. During development, there will be some comments relating to speccing out the issue and probably some code-review type comments on the pull request itself. It would be beyond convenient if all of those were connected into one discussion. There might be multiple pull requests involved in a single issue, and they should be linked with statuses on the issue itself.
It's a pain to have the discussion, code review, and resolution split between the issue and the pull request. They need to all be integrated together."