setClassName should not remove the class by default...

By default the **Ink.Dom.Css.setClassName** method was removing the class from the element...

IMO that 3rd parameter shouldn't be there at all and the method should completely replace the element's className attribute with the one provided. If I wanted to make an incremental change, I'd use the add/remove/toggle methods (that already exist, so I'm really having trouble to find why this method behaves like it does - legacy stuff, perhaps?).

I'd like to change the method's signature/behavior completely, but I want to get some feedback before I do. :)