Replace action sprite with FontAwesome

Summary: Replaces the action icons in action headers with FontAwesome

Test Plan:
- grep SPRITE_ACTIONS
- grep sprite-actions
- Replace on UIExamples
- Replace on Workboards
- Replace on Dashboards
- Replace on FeedStories

{F157840}
{F157841}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9230