Port Restaurant Demo to Scala

[replomancer]

This demo from the Java library:
https://github.com/google/differential-privacy/tree/master/examples/java
has already been ported to Clojure:
https://github.com/OpenMined/JavaDP/blob/master/doc/clojure/ClojureRestaurantDemo.ipynb

We should also add a Scala version of this demo.

Here's another Scala notebook for reference: https://github.com/OpenMined/JavaDP/tree/master/doc/scala

It's not small, but it can be a good first issue.