Ability to RSVP to event
Summary: Closes T7986, Ability to RSVP to event.
Test Plan: Create event, invite users, invited users should see buttons on event detail header to accept/decline. Accepting/declining reflects in the invitee status in the property list.
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T7986
Differential Revision: https://secure.phabricator.com/D12619