Update spring-security-oauth2 to 2.0.2 and spring to 4.0.3

This pull request closely follows the "spring upgrade" branch from April this year and upgrades spring to 4.0.3, security to 3.2.3 and oauth2 to 2.0.2. 
I also noticed that the version of jetty was 9.x which requires jdk7 so I changed the jetty version from 9.x to the latest 8.x from April 2014 (not too old) which requires jdk6. I am using the client in addition to the server and the openid-connect-server-webapp appears to function correctly with these changes applied.