function addScene(title,initfunc){
        if(typeof(title) !== "string"){
            throw new Error("1st argument of Demo.addScene(title,initfunc) must be a string!");
        }
        if(typeof(initfunc)!=="function"){
            throw new Error("2nd argument of Demo.addScene(title,initfunc) must be a function!");
        }
        scenes.push(initfunc);
        var idx = scenes.length-1;
        scenePicker[title] = function(){
            changeScene(idx);
        };
        sceneFolder.add(scenePicker,title);
    }
Add a scene to the demo app
@method addScene
@param {String} title Title of the scene
@param {Function} initfunc A function that takes one argument, app, and initializes a physics scene. The function runs app.setWorld(body), app.addVisual(body), app.removeVisual(body) etc.