Extend Config to full-width

Summary:
Ref T13362. Some applications moved to fixed-width a while ago but I was generally unsatisfied with where they ended up and have been pushing them back to full-width.

Push Config back to full-width. Some of the subpages end up a little weird, but this provides more space to work with to make some improvements, like makign `maniphest.statuses` more legible in the UI>

Test Plan: Grepped for `setFixed(`, updated each page in `/config/`. Browsed each controller, saw workable full-width UIs.

Maniphest Tasks: T13362

Differential Revision: https://secure.phabricator.com/D20925

src/applications/config/controller/PhabricatorConfigCacheController.php

@@ -33,13 +33,12 @@ final class PhabricatorConfigCacheController
 
     $content = id(new PHUITwoColumnView())
       ->setHeader($header)
-      ->setNavigation($nav)
-      ->setFixed(true)
-      ->setMainColumn($page);
+      ->setFooter($page);
 
     return $this->newPage()
       ->setTitle($title)
       ->setCrumbs($crumbs)
+      ->setNavigation($nav)
       ->appendChild($content);
   }