Update notification UI a little

Summary: Fixes T8944. Adds a small dot if notification is new along with color. Goes away when clicked. Increased font and padding for readability.

Test Plan: Send notifications from test account, review them in menu, application search, and in real-time display.

Reviewers: epriestley

Reviewed By: epriestley

Spies: Korvin

Maniphest Tasks: T8944

Differential Revision: https://secure.phabricator.com/D18485