Remove old Phrequent propery rendering code and show "Time Spent" in higher precision

Summary:
See https://discourse.phabricator-community.org/t/how-to-get-total-time-spent-on-a-task-in-minutes-or-hours/2241.

Phrequent has two nearly-identical copies of its rendering code: one for old "property event" objects and one for newer "curtain" objects. In the upstream, both trackable object types (tasks and revisions) use curtains, so throw away the old code since it isn't reachable. Third-party trackable objects can update to the curtain UI, but it's unlikely they exist.

Render the remaining curtain UI with more precision, so we show "Time Spent: 2d, 11h, 49m" instead of "Time Spent: 2d".

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19927