This is to somehow make it clearer that those classes deal with handling of properties only.
Actually, too late anyhow as you have already committed this. Never mind ... .
One more thing: this patch unfortunately changes public API, as there's people out there who manually set e.g. XML properties on the (Un-)Marshaller using e.g. XMLConfiguration.SOME_CONSTANT. As bad as this is, I think there's no way aorund this. Unless, of course, you want to just deprecate the *Configuration classes. I leave this up to you.
Great, As I am about to commit one or two more patches that will introduce a new property, how about committing this as soon as possible (before we make our life harder than necessary) ?