[feature/avatars] Move avatar specific settings to drivers

PHPBB3-10018

phpBB/includes/avatar/driver/interface.php

@@ -62,6 +62,13 @@ interface phpbb_avatar_driver_interface
 	**/
 	public function prepare_form($template, $row, &$error);
 
+	/**
+	* Prepare form for changing the acp settings of this avatar
+	*
+	* @return array Return the array containing the acp settings
+	**/
+	public function prepare_form_acp();
+
 	/**
 	* Process form data
 	*