Revert "Remove PHUICalendarWidgetView"
Summary: This reverts commit 8ce8a761efe9995c371727fdfe9b9e5d7d1b4592.
Test Plan: N/A
Reviewers: chad, #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D12573