[ticket/10586] Change the interface to an abstract class

This allows the common phpBB objects to be automatically accessible to
extensions without the author having to globalize and assign each one
himself. This is better because it also gives purpose to the
phpbb_extension_controller class; instead of just being the way to
ensure a handle() method is present, it also does this work for us.

PHPBB3-10586

phpBB/includes/extension/controller_interface.php

@@ -1,31 +0,0 @@
-<?php
-/**
-*
-* @package extension
-* @copyright (c) 2011 phpBB Group
-* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
-*
-*/
-
-/**
-* @ignore
-*/
-if (!defined('IN_PHPBB'))
-{
-	exit;
-}
-
-/**
-* The interface that extension classes have to implement to run front pages
-*
-* @package extension
-*/
-interface phpbb_extension_controller_interface
-{
-	/**
-	* handle the request to display a page from an extension
-	*
-	* @return	null
-	*/
-	public function handle();
-}