Refine "Tactical Command" layout and styling

Summary:

• Move the buttons in the jump nav to iOS-style "application" buttons in the

header. These are sort of ugly right now, but I think serviceable enough. Some
day we will hire a designer whose entire job is to pick up after me.

• This gives us more room (allowing us to restore "Maniphest" and

"Differential").

• This also disassociates the app buttons from the jump nav, which was a

point of confusion (user expectation that the text input is related to the
buttons).

• Allow "Active Revisions" and "Assigned Tasks" to collapse completely. They

didn't completely collapse before because the top-level "Active Tasks" / "Active
Revisions" was sort of overloaded as quick nav to apps. Now we have app buttons.

• Reduce overall size of jump nav.

Test Plan: Looked at homepage in various states of need-for-attention.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1694