Throw instead of log for invalid properties

Summary: Continue work started at D3601.

Test Plan:
Commented declaration `AphrontController::$request`, saw exception.
Brought it back, didn't see exception.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4233

src/aphront/AphrontController.php

@@ -3,7 +3,7 @@
 /**
  * @group aphront
  */
-abstract class AphrontController {
+abstract class AphrontController extends Phobject {
 
   private $request;
   private $currentApplication;
@@ -45,9 +45,4 @@ abstract class AphrontController {
     return $this->currentApplication;
   }
 
-  public function __set($name, $value) {
-    phlog('Wrote to undeclared property '.get_class($this).'::$'.$name.'.');
-    $this->$name = $value;
-  }
-
 }