Left nav should no longer offer to create Calendar event and create event page should no longer show left nav.

Summary: Closes T7934, Left nav should no longer offer to create Calendar event and create event page should no longer show left nav.

Test Plan: Open Calendar, left nav should be missing the Create Event option, create event, create view should no longer show left nav.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7934

Differential Revision: https://secure.phabricator.com/D12638