Add Conpherence sprites.

Summary: Let's see if I did this right. This adds on and off state icons (1 and 2x) for conpherence. I think I need to tweak and add more CSS to have the off hover state be the on icon. Will check.

Test Plan: spritegen

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2400

Differential Revision: https://secure.phabricator.com/D4709