Update inline-comment styles in Differential

Summary:
Moderize Inline Comment Display

 - Use standard colors
 - Better display with/without comment
 - OMG Icons

Test Plan:
{F148256}

Test with and without main comment, test with many for few comments on 1-3 files.

Reviewers: epriestley, btrahan

Reviewed By: btrahan

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8885