HOLD: Feedback faves and flags

This is the PR for the feedback faves and flags.

Related:
* https://github.com/GigaOM/gigaom-plugins/pull/2574
* https://github.com/GigaOM/gigaom/pull/5157

See: https://github.com/GigaOM/gigaom/milestones/Comment%20redesign%20v3:%20faves%20and%20flags
The content of this email doesn't match the ticket https://github.com/GigaOM/gigaom/issues/5153