Link proxy column headers on workboards to proxied projects

Summary: Ref T10010. Allows you to click "Milestone 99" to jump directly to that project.

Test Plan:
  - Clicked milestone header, went to milestone.
  - Clicked normal column header, nothing happened. Wow!

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10010

Differential Revision: https://secure.phabricator.com/D15204

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -281,6 +281,13 @@ final class PhabricatorProjectBoardViewController
         ->setSubHeader($column->getDisplayType())
         ->addSigil('workpanel');
 
+      $proxy = $column->getProxy();
+      if ($proxy) {
+        $proxy_id = $proxy->getID();
+        $href = $this->getApplicationURI("view/{$proxy_id}/");
+        $panel->setHref($href);
+      }
+
       $header_icon = $column->getHeaderIcon();
       if ($header_icon) {
         $panel->setHeaderIcon($header_icon);