Events - add a byline to event list

Summary: so you can see who the event is about...! Fixes T5621.

Test Plan: saw the creator of each event on /calendar/event/query/all/

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5621

Differential Revision: https://secure.phabricator.com/D10169