Update to latest version of multi-project gradle template

This addresses the issue of attempting to resolve artifacts from raw.github.com (instead using bintray) as well as picking up all the other enhancements that have rolled into gradle-template

I've tested the following scenarios successfully:

* perform a clean build
* run the server and client as per the wiki docs
* execute the uploadMavenCentral task (with a local file URL override for the snapshotRepository)