Add headericons a little more consistently

Summary: I kinda like these to differentiate the headers and different object types. Somethings duplicitive, but helps orient the clean header a bit.

Test Plan: Review each in sandbox.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15394

src/applications/countdown/controller/PhabricatorCountdownViewController.php

···
       ->setHeader($title)
       ->setUser($viewer)
       ->setPolicyObject($countdown)
-      ->setStatus($icon, $color, $status);
+      ->setStatus($icon, $color, $status)
+      ->setHeaderIcon('fa-rocket');
 
     $actions = $this->buildActionListView($countdown);
     $properties = $this->buildPropertyListView($countdown);

src/applications/ponder/controller/PonderQuestionViewController.php

···
     $header->setHeader($question->getTitle());
     $header->setUser($viewer);
     $header->setPolicyObject($question);
+    $header->setHeaderIcon('fa-university');
 
     if ($question->getStatus() == PonderQuestionStatus::STATUS_OPEN) {
       $header->setStatus('fa-square-o', 'bluegrey', pht('Open'));

src/applications/slowvote/controller/PhabricatorSlowvotePollController.php

···
       ->setHeader($poll->getQuestion())
       ->setUser($viewer)
       ->setStatus($header_icon, $header_color, $header_name)
-      ->setPolicyObject($poll);
+      ->setPolicyObject($poll)
+      ->setHeaderIcon('fa-bar-chart');
 
     $actions = $this->buildActionView($poll);
     $properties = $this->buildPropertyView($poll);