Correct included JAXB version.

Java 7 includes a JAXB version (2.2.4-2) more recent than the one we put in endorsed/ (2.0). We should probably remove it and also upgrade the jaxb-impl we use.

Metro devs recommend using the latest JAXB in any case (if compatible with the rest of our stack): https://java.net/projects/jaxb/lists/users/archive/2013-01/message/9

To check included version in a JDK: http://marxsoftware.blogspot.fr/2011/03/new-xml-stack-in-jdk-7.html

The old version of jaxb-api also prevents aws-java-sdk from working correctly, see stack trace in comments.