JIRA Integration: Link and/or Comment

Summary:
Current JIRA integration is quite noisy in terms of email, and makes users hunt and peck for the related revisions.

Teach it to create an Issue Link on the JIRA side, and allow to disable commenting.

Test Plan: comment on revision in each of the 4 settings, check JIRA end for expected result.

Reviewers: btrahan, eMxyzptlk, epriestley, #blessed_reviewers, avivey

Reviewed By: epriestley, #blessed_reviewers

Subscribers: avivey, vhbit, jra3, eMxyzptlk, frenchs, aik099, svemir, rmuslimov, cpa199, waynea, epriestley, Korvin, hach-que

Projects: #doorkeeper

Maniphest Tasks: T5422

Differential Revision: https://secure.phabricator.com/D9858