feature: support multiple application on single server

```java
class FooApp extends Jooby {
   {
      setContextPath("/foo");
      get("/hello", ...)
   }
}

class BarApp extends Jooby {
   {
      setContextPath("/bar");
      get("/hello", ...)
   }
}
```

```java

main(String[] args) {
   runApp(args, new NettyServer(), List.of(FooApp::new, BarApp::new))
}
```

Apps will share the server, but they are standalone/independent applications.
