R1:3e7a7518faf6

Add missing Conpherence icon + generate hovers

Summary: Added missing sprite images and added hover classes to sprite generator class.

Test Plan: read the CSS

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4721