In "Move Tasks to Column...", show only visible columns

Summary:
See PHI94. I considered this initially but wasn't sure about it. However, PHI94 brings up the good point that we already use a similar rule in Maniphest.

For consistency, only show visible columns here too.

Test Plan: Used "Move tasks to column..." on a board with visible and hidden columns, only saw visbile columns offered in the dropdown.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18668

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -313,6 +313,12 @@ final class PhabricatorProjectBoardViewController
           $columns = $move_engine->getColumns($move_project->getPHID());
           $columns = mpull($columns, null, 'getPHID');
 
+          foreach ($columns as $key => $column) {
+            if ($column->isHidden()) {
+              unset($columns[$key]);
+            }
+          }
+
           $move_column_phid = $request->getStr('moveColumnPHID');
           if (!$move_column_phid) {
             if ($request->getBool('hasColumn')) {