Fixed corrupted artifacts upload during deploy and improved Dockerfile.

Artifact upload during deployment to NEXUS server was corrupted: the file was uploaded
with multipart, and multipart contant where stored. This is fixed.
The deploy is improved by generating a sha1 sum that is upload to NEXUS with the JAR.
The Dockerfile is improved by checking the sha1 and running the app for help to check
Java is found, able to load the jar and run java main().