Calendar day view should have forward/back controls to scroll through days

Summary: Ref T4393, Calendar day view should have forward/back controls to scroll through days

Test Plan: Open day view on first or last day of the month, scrolling backwards or forwards through days should correctly calculate the date of the next day and the previous day and correctly find events.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T4393

Differential Revision: https://secure.phabricator.com/D12721