Node's listeners should execute on node scope - remove self param from func signature

Take "picked" listeners for example:

SceneJS.node({
            sid: "alpha",
 
            listeners: {
                "picked":{
                    fn: function(self, params) {
                         alert(self.getSID() + " handling 'picked' event from " + params.uri);
                    }
                }
            }
        },

We dont need the self param - remove it to keep things terse, just fire the listener on the node scope:

SceneJS.node({
            sid: "alpha",
 
            listeners: {
                "picked":{
                    fn: function(params) {
                         alert(this.getSID() + " handling 'picked' event from " + params.uri);
                    }
                }
            }
        },