R1:af07600aaac7

Make Differential objective markers show a brighter "editing" state

Summary:
Ref T12733.

- While editing a comment, show a pink star ({icon star, color=pink}) with a tooltip.
- Slight UI tweaks, including draft comments getting an indigo pencil ({icon pencil, color=indigo}).

Test Plan: {F4968470}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12733

Differential Revision: https://secure.phabricator.com/D17977