On workboards, link ancestor project breadcrumbs to their workboards

Summary:
Ref T13269. Currently, if you're on a milestone workboard like this:

> Projects > Parent > Milestone > Workboard

The "Parent" link goes to the parent profile. More often, I want it to go to the parent workboard. Try doing that? This is kind of one-off but I suspect it's a better rule.

Also, consolidate one billion manual constructions of "/board/" URIs.

Test Plan: Viewed a milestone workboard, clicked the parent link, ended up on the parent workboard.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13269

Differential Revision: https://secure.phabricator.com/D20331

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -726,7 +726,7 @@ final class PhabricatorProjectBoardViewController
       ->setType(PHUIListItemView::TYPE_DIVIDER);
     $fullscreen = $this->buildFullscreenMenu();
 
-    $crumbs = $this->buildApplicationCrumbs();
+    $crumbs = $this->newWorkboardCrumbs();
     $crumbs->addTextCrumb(pht('Workboard'));
     $crumbs->setBorder(true);