cookie session store

Next release will have a `client side` session store, where data will be persisted as cookie.

``` java
{
  cookieSession();

  get("/", req -> {
    Session session = req.session();
    session.set("foo", "bar");
    return "OK";
  });
}
```

This feature requires an `application.secret` in order to sign (not encrypt) the cookie 
