Increased visibility of mouse related nifty-renderer-slick input events

Hi

I am writing an alternative system to handle the `InputEvent`'s generated from Nifty/Slick2d, and found that the mouse related events have fields that are not visible from the outside. This makes it impossible to create a custom `AbstractSlickInputSystem`, as you cannot access the information contained in each event.

Would it be possible to increase the visibility of these fields (and add getters where necessary) ? 

Simon