R1:adca2698128c

Add gradient to object-list cards

Summary: Adds a gradient, also re-ran sprite generator to attempt to sprite - for some reason all images were un-optimized.

Test Plan: Test on UI Examples page

Reviewers: epriestley, btrahan

Reviewed By: btrahan

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5354