Add basic support for new navigation menu

Summary:
Add a new left-side application menu. This menu shows which application you're in and provides a quick way to get to other applications.

On desktops, menus are always shown but the app menu can be collapsed to be very small.

On tablets, navigation buttons allow you to choose between the menus and the content.

On phones, navigation buttons allow you to choose between the app menu, the local menu, and the content.

This needs some code and UI cleanup, but has no effect yet so I think it's okay to land as-is, I'll clean it up a bit as I start integrating it. I want to play around with it a bit and see if it's good/useful or horrible anyway.

Test Plan: Will include screenshots.

Reviewers: vrana, btrahan, chad

Reviewed By: btrahan

CC: aran, alanh

Maniphest Tasks: T1569

Differential Revision: https://secure.phabricator.com/D3223

src/applications/base/PhabricatorApplication.php

@@ -62,6 +62,10 @@ abstract class PhabricatorApplication {
     return true;
   }
 
+  public function getCoreApplicationOrder() {
+    return null;
+  }
+
 
 /* -(  URI Routing  )-------------------------------------------------------- */