Fix retrun type of getColumn in Column_Renderer_Interface (#1713)

* Fix retrun type of getColumn in Column_Renderer_Interface

Fixes multiple issues spotted by phpstan

* Fix return type of getColumn

* Set type for setColumn in Column_Renderer_Interface

Author: tmotyl

app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Interface.php

@@ -38,7 +38,7 @@ interface Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Interface
      * Set column for renderer
      *
      * @abstract
-     * @param $column
+     * @param Mage_Adminhtml_Block_Widget_Grid_Column $column
      * @return void
      */
     public function setColumn($column);
@@ -47,7 +47,7 @@ public function setColumn($column);
      * Returns row associated with the renderer
      *
      * @abstract
-     * @return void
+     * @return Mage_Adminhtml_Block_Widget_Grid_Column
      */
     public function getColumn();