Show all available action list icons in UIExamples

Summary:
Make the example page a little more useful by showing available icons.

Also replace the "new" image, it had a little arrow which I thought was a "+". Use the one with a "+".

Test Plan: {F21966}

Reviewers: btrahan, vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3794