Respect phriction.enabled in config

Summary: Eventually we'll have a real "uninstall" sort of thing, but until we do we should keep respecting this flag.

Test Plan: Disabled the flag, saw Phriction vanish from the application list.

Reviewers: btrahan, vrana

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D3724

src/applications/phriction/application/PhabricatorApplicationPhriction.php

@@ -34,6 +34,10 @@ final class PhabricatorApplicationPhriction extends PhabricatorApplication {
     return PhabricatorEnv::getDoclink('article/Phriction_User_Guide.html');
   }
 
+  public function isEnabled() {
+    return PhabricatorEnv::getEnvConfig('phriction.enabled');
+  }
+
   public function getRoutes() {
     return array(
       // Match "/w/" with slug "/".