R1:b56001457785

Revamp inline commenting UI

Summary:
Rebuilds the UI in Differential commenting. Specifically we look at the following design patterns:

**To the author:**
- The author of the diff should be able to easily identify what comments are done and not done.
- We keep undone comments yellow
- Clicking done turns comment block into 'unsubmitted state'

**To the reviewer:**
- Easier understanding of unsubmitted states
- All conversations to be yellow/important

**Todo**
- Not all color CSS states correct…