Conpherence - add createthread method

Summary: Ref T3166. I moved the create logic into a static method in the editor class to keep things tidy.

Test Plan: created a conpherence from UI. purdy. tried errors and got UI to show "required". for conduit, created a thread with all the bells and whistles and it worked. verified i got proper exceptions with bum conduit calls

Reviewers: epriestley

Reviewed By: epriestley

CC: chad, aran, Korvin

Maniphest Tasks: T3166

Differential Revision: https://secure.phabricator.com/D6083

src/applications/base/controller/PhabricatorController.php

@@ -141,7 +141,7 @@ abstract class PhabricatorController extends AphrontController {
     if (!$this->getCurrentApplication()) {
       throw new Exception("No application!");
     }
-    return $this->getCurrentApplication()->getBaseURI().ltrim($path, '/');
+    return $this->getCurrentApplication()->getApplicationURI($path);
   }
 
   public function buildApplicationPage($view, array $options) {