WIP: java servlet example

FOR REVIEW ONLY

This is a working example app that registers a couple servlet handlers with the Jetty service.
Note the introduction of Java code under `src/`.

Implementation adapted from: http://examples.javacodegeeks.com/enterprise-java/jetty/embedding-jetty-with-servlet/

We should decide if we want to add this `add-servlet-handler` function to our jetty service, and if we're going to keep an example app with a Java servlet, where do we put the Java code?