Add option for printing changes grouped by issue

This also adds support for V8 project on issue tracker.

R=tandrii@chromium.org

Change-Id: Ie90ae664573d36030267b639e8a55bc349cad872
Reviewed-on: https://chromium-review.googlesource.com/966623
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>