Fix SceneJS.WithData arguments

WithData node does not seem to support the standard Node configuration signature.

This works:

return new SceneJS.WithData(
    {
        param1: "foo",
        param2 : "bar" 
    },
    new SceneJS.Node());

But this does not:

return new SceneJS.WithData(
    {
        sid: "wibble"
    },
    {
        param1: "foo",
        param2 : "bar" 
    },
    new SceneJS.Node());