Allow workboards to be filtered with ApplicationSearch

Summary:
Ref T4673.

IMPORTANT: I had to break one thing (see TODO) to get this working. Not sure how you want to deal with that. I might be able to put the element //inside// the workboard, or I could write some JS. But I figured I'd get feedback first.

General areas for improvement:

  - It would be nice to give you some feedback that you have a filter applied.
  - It would be nice to let you save and quickly select common filters.
  - These would probably both be covered by a dropdown menu instead of a button, but that's more JS than I want to sign up for right now.
  - Managing custom filters is also a significant amount of extra UI to build.
  - Also, maybe these filters should be sticky per-board? Or across all boards? Or have a "make this my default view"? I tend to dislike implicit stickiness.

Test Plan:
Before:

{F157543}

Apply Filter:

{F157544}

Filtered:

{F157545}

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: qgil, swisspol, epriestley

Maniphest Tasks: T4673

Differential Revision: https://secure.phabricator.com/D9211

src/applications/search/controller/PhabricatorApplicationSearchController.php

@@ -90,7 +90,7 @@ final class PhabricatorApplicationSearchController
 
     if ($request->isFormPost()) {
       $saved_query = $engine->buildSavedQueryFromRequest($request);
-      $this->saveQuery($saved_query);
+      $engine->saveQuery($saved_query);
       return id(new AphrontRedirectResponse())->setURI(
         $engine->getQueryResultsPageURI($saved_query->getQueryKey()).'#R');
     }
@@ -145,7 +145,7 @@ final class PhabricatorApplicationSearchController
 
       // Save the query to generate a query key, so "Save Custom Query..." and
       // other features like Maniphest's "Export..." work correctly.
-      $this->saveQuery($saved_query);
+      $engine->saveQuery($saved_query);
     }
 
     $nav->selectFilter(
@@ -353,18 +353,6 @@ final class PhabricatorApplicationSearchController
       ));
   }
 
-  private function saveQuery(PhabricatorSavedQuery $query) {
-    $query->setEngineClassName(get_class($this->getSearchEngine()));
-
-    $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
-    try {
-      $query->save();
-    } catch (AphrontQueryDuplicateKeyException $ex) {
-      // Ignore, this is just a repeated search.
-    }
-    unset($unguarded);
-  }
-
   protected function buildApplicationMenu() {
     return $this->getDelegatingController()->buildApplicationMenu();
   }