Changed event hook to an enum that manages a collection of event handlers. There are now global event delgators for each event type. If a component is interested in being notified of an event they should register a handler with that event. one of the motivations of implementing the EventHook in this way is that we needed to handle modifying line numbers to be one based (and the RETURN type ine number for ruby needs to be offset by 2). If these rules ever change we can change them here.