Put application curtain panels above extension curtain panels

Summary:
Ref T13528. The original rationale here was that it's easier to find items at the bottom of the curtain than somewhere in the middle, since they're in a more clearly predictable visual location.

This might be true in some sense, but user feedback about this has fairly consistently indicated that the layout is surprising. Try the other order. See also D20967 for some discussion.

In practice, this primarily moves "Author / Assigned" above other panel elements in Maniphest.

Test Plan: Looked at tasks, aw "Author / Assigned" above "Tags / Subscribers".

Maniphest Tasks: T13528

Differential Revision: https://secure.phabricator.com/D21200