Provide transaction strings, icons and colors for Differential

Summary: Ref T2222. Once these are live, yell if any of them seem off. I tried to mostly stay consistent-ish with what we had before.

Test Plan: Looked at a bunch of revisions and saw more detailed, colorful transactions.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8223