Create artifact with shaded guava library

[andreaslang]

Hi, this is in the first instance for discussion. There might be better ways of doing this.

What I am trying to do here is to produce an artifact with a shaded guava library. Many clusters provide a terribly old version of guava (15.0). Which is a mess to sort out usually. An easy way around it is to produce a shaded version of it. The maven plugin creates a new artifact "spark-dynamodb-0.0.13-shaded-guava.jar" in which it moves packages so that com.google.common becomes shaded.com.google.common. This allows the jar to be deployed using a new guava version without affecting the rest of the cluster.

It would be cool to have this produced automatically so that I don't need to maintain a fork. I am fairly sure other people would find it useful, too. In my specific use-case I needed it to make it work on AWS Glue, as the DynamicFrame connector was not flexible enough.

Happy to discuss and adapt as needed.