Update of Force MVC to work with new version of Force Webserver and DartVoid

Created a more clear directory structure. Added some more comments to server.dart. 

With the help of the new version of Force Webserver, this example can choose to either serve static content or to let a web server handle that load. It is set with the parameter "clientServe", if it's true Force handles all serving, if it's false then a webserver can take over and serve the client code and let Force get all performance for server side processing. With the help of this the exact same code runs out of the box on localhost and DartVoid without any changes (some small setup in app.yaml is also needed of course). 

Even if dart can serve static content, it will always have a hard time competing with Nginx and at best be comparable. If you add to that the fact that Dart today can't run on more than one core it can mean a lot to performance to let a webserver take some of the load on a production app, especially if there is very little setup.