Creates deb package as part of build

[gehel]

This creates a minimal .deb package that could be used to deploy just this jar to the system. This should help in deploying gelfj outside of java packaging. In my case, the goal is to deploy it to our elastic search cluster, which is itself deployed as a .deb.

I'd love to have this packaging done upstream and not create specific packages for our use case. Let me know...