Added Gradle plugin.

We have added a new Maven module which is a Gradle plugin with very similar functionality to the Maven plugin that already existed. We also added the module to the parent pom and added instructions on how to use the Gradle plugin in the readme file.

We have not worried about the JavaScript execution as the Gradle build file support Groovy which gives us the functionality to build our own custom build number.

Is there anything we need to do to get this published to the Maven Repo?