Create an examples/java and examples/java8 uber jar that doesn't contain a runner

In addition to the regular artifact examples/java and examples/java8 that are produced, consider making an uber jar as an additional attached artifact that shades all the dependencies for easier command line usage so that it can be joined with a runner uber jar.
```

java -cp examples.jar:myrunner.jar WordCount ...

```

Also look at the maven archetypes found in:
https://github.com/apache/beam/tree/master/sdks/java/maven-archetypes

Imported from Jira [BEAM-2251](https://issues.apache.org/jira/browse/BEAM-2251). Original Jira may contain additional context.
Reported by: lcwik.

Start by examining how the examples/java and examples/java8 artifacts are produced, then review the Maven archetypes under sdks/java/maven-archetypes. Verify the packaging flow for the requested dependency-shaded artifacts and use the shown java -cp invocation as the usage check; done means both additional artifacts are attached without including a runner.

Written by the indexing model from the issue text.