Labeled controls always return computed minHeight

Currently LabelSkinBase's computeMinHeight() method executes almost the same logic as computePrefHeight(), except that it uses the graphic's minHeight instead of it's pref. The problem with this is that if the application overrides a labeled control's prefHeight (button.setPrefHeight(10)), it's min height might be greater than it's pref height and the overridden pref height will be disregarded and the app will wonder why. It might be preferable to have computeMinHeight() simply return getControl().prefHeight(w) and not worry about the Graphic min vs pref size.