Conpherence calendar updates

Summary: Fixes T3253 by shifting the display to the "next 3 days". Also adds in the "create" functionality for calendar on desktop view only, ref T3251. As part of T3251, I plan to make this work on mobile too.

Test Plan: added statuses and noted errors showed up. noted on success the widget pane refreshed. also made sure the regular old /calendar/status/create/ page still worked.

Reviewers: epriestley

Reviewed By: epriestley

CC: chad, aran, Korvin

Maniphest Tasks: T3251, T3253

Differential Revision: https://secure.phabricator.com/D6072