CF-165/CF-293: add versioning and release process to preferences-service

This PR will add the version to the artifacts and jars output when you do ```gradle build```. 

I also added a plugin for managing the release of this component and the uploading of the released artifacts to our Nexus. However, I could not fully test this until I have the Jenkins job set up. And I can't set the Jenkins job up without talking to Alex first to figure out how we can pass in the Nexus username/password properly. 

As long as you don't run ```gradle release``` the changes should be benign. 

The new plugins I added does require the use of Gradle 2.2. Grade 1.x will not work.