Restyle username/password login for reduced hideousness

Summary: Ref T1536. Error state is a bit gross but we need to sort that out in general.

Test Plan:
{F46549}

{F46550}

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T1536

Differential Revision: https://secure.phabricator.com/D6208

src/applications/base/controller/PhabricatorController.php

@@ -228,6 +228,8 @@ abstract class PhabricatorController extends AphrontController {
         $response->setContent($view->render());
         return $response;
       } else {
+        $response->getDialog()->setIsStandalone(true);
+
         return id(new AphrontAjaxResponse())
           ->setContent(array(
             'dialog' => $response->buildResponseString(),