Fix an issue with creating tasks directly into milestone columns

Summary:
These columns were conflating `projectPHID` (the defualt project to add to the task) with `boardPHID` (the board the column appears on).

Separate them to fix the beahvior.

Test Plan: Used "Add Task" from dropdown menu of a milestone column on a parent project's workboard.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D15242

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -720,6 +720,7 @@ final class PhabricatorProjectBoardViewController
       ->setMetadata(
         array(
           'columnPHID' => $column->getPHID(),
+          'boardPHID' => $project->getPHID(),
           'projectPHID' => $default_phid,
         ));