Download smoketest JAR file with all dependencies

Since the parent-pom and base-bom projects are both packaged with "pom" packaging and as such don't contain any actual source code, it's easy for non-obvious configuration bugs to slip through which don't affect them, but immediately break projects with actual source code. The purpose of this module is to provide a minimal example of a jar maven project which exercises various pieces of maven functionality, to ensure that no easily detectable issues slip through.