Add Gradle-based build and/or release scripts

A suggestion was made to enhance the build process by provding a Gradle-based script (see www.gradle.org) in order to streamline the build process and provide better integration with maven. There is also the possibility of changing the release building scripts from shell-based (for *nix or OSX systems) to Gradle so they will be cross-platform.
Gradle is a complete Ant superset, so the beginning could be a simple wrapper around the current "build.xml", and then migrate over time.
We also need to see if Jenkins has a Gradle 1.6 plugin available for the CI builds.