Add a 'create' policy to Project

Summary: UX on this could probably be better 'disabled' crumbs don't appear to have any visible difference, and the policy error has to load the /create page rather than being a modal - not sure on the way to fix these.

Test Plan: Tried to create a project with and without access, saw suitable error.

Reviewers: epriestley, #blessed_reviewers

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7279

src/applications/project/controller/PhabricatorProjectController.php

@@ -24,11 +24,16 @@ abstract class PhabricatorProjectController extends PhabricatorController {
   public function buildApplicationCrumbs() {
     $crumbs = parent::buildApplicationCrumbs();
 
+    $can_create = $this->hasApplicationCapability(
+      ProjectCapabilityCreateProjects::CAPABILITY);
+
     $crumbs->addAction(
       id(new PHUIListItemView())
         ->setName(pht('Create Project'))
         ->setHref($this->getApplicationURI('create/'))
-        ->setIcon('create'));
+        ->setIcon('create')
+        ->setWorkflow(!$can_create)
+        ->setDisabled(!$can_create));
 
     return $crumbs;
   }