mavenization of appengine-awt

XDocreport (https://code.google.com/p/xdocreport/) is deployed to central maven repo.

We aim to develop a create a GAE capable extension.

It's a good practice to mavenize all possible dependency.

Here is my suggestion for mavenization.

CI can be found here : https://opensagres.ci.cloudbees.com/view/xdocreport/job/appengine-awt/