Expose all callbacks in the inspector. and 2+ static parameters methods support.

So far every thing has been great linking callbacks directly to script. but only one callback is supported max and only works with actions and one-parameter methods. Event Trigger component is a marvelous surprise but it has only a specific list for general behavior like OnPointerEnter, etc.
For instance UnityEngine.UI.Slider.OnBeginDrag() isn't exposed whether in the slider component or in the event trigger component. so I have to attach a script to the slider.