Make default and hidden columns in Workboards more clear

Summary: Fixes T6469. Changes the default icon into text instead. Added the text to hidden boards and now display when reordering as well.

Test Plan:
Moved a bunch of columns, tested reordering. Seems more clear.

{F229626}

{F229627}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6469

Differential Revision: https://secure.phabricator.com/D10784

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -227,6 +227,7 @@ final class PhabricatorProjectBoardViewController
 
       $panel = id(new PHUIWorkpanelView())
         ->setHeader($column->getDisplayName())
+        ->setSubHeader($column->getDisplayType())
         ->addSigil('workpanel');
 
       $header_icon = $column->getHeaderIcon();