Remove CellTrait from controller.

Since it isn't going to be used frequently from controllers, freeing up
the cell() method is useful and currently contentious. If we find
ourselves using cells in controllers frequently we can always re-include
the trait.

Refs #3487

src/Controller/Controller.php

@@ -30,7 +30,6 @@
 use Cake\Routing\Router;
 use Cake\Utility\Inflector;
 use Cake\Utility\MergeVariablesTrait;
-use Cake\View\CellTrait;
 use Cake\View\View;
 use Cake\View\ViewVarsTrait;
 
@@ -79,7 +78,6 @@
  */
 class Controller implements EventListener {
 
-	use CellTrait;
 	use LogTrait;
 	use MergeVariablesTrait;
 	use ModelAwareTrait;