Use G+ to fetch the user's profile and store it in the session. Also verifies that they really did log in.
Move Google client ID into jetty-env.xml

Here it can be overridden by the local servlet container configuration. I think it's safe to include it in VCS since you can only use it to log into a local test server (eg. localhost:8080). When I stand up a production server it will be able to use a different client ID. This change also makes it easier for others to try out the code. You should now be able to just clone it out of git and do mvn jetty:run and it'll work.