Added default language pack (en-gb)

admin/error/not_found.php

@@ -0,0 +1,6 @@
+<?php
+// Heading
+$_['heading_title']  = 'Page Not Found!';
+
+// Text
+$_['text_not_found'] = 'The page you are looking for could not be found! Please contact your administrator if the problem persists.';

admin/error/permission.php

@@ -0,0 +1,6 @@
+<?php
+// Heading
+$_['heading_title']   = 'Permission Denied!';
+
+// Text
+$_['text_permission'] = 'You do not have permission to access this page, please refer to your system administrator.';