Convert to using gradle-multi-project-example structure

[cdancy]

The current gradle design was a quick and easy win but we need something a bit more robust. The gradle-multi-project-example is something we worked on internally and I open-sourced for the greater community. We should adopt this model as it has built in support for shadow/uber/all jars (which this project uses), a complete end-to-end release process, baked in static analysis tools, and loads of other bells and whistles.