Calendar event detail view should show no time for all day events, and should show only one time field for one day events.

Summary: Ref T8021, Calendar event detail view should show no time for all day events, and should show only one time field for one day events

Test Plan: Open all-day event, event should show "Time" field with not start/end dates. Two day events should show start and end days, not times. Normal events should show old way of displaying start and end times.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8021

Differential Revision: https://secure.phabricator.com/D12768