Adding the first Gradle project.

Gradle is another alternative for builds, just like Ant or Maven.

Content and features:
 * It contains a Java project that uses Gradle for building
 * Gradle uses maven repo to resolve the dependencies
 * Creates an executable jar with Hello class as the main one
 * Includes the build.gradle that packages the jar with its dependencies
 * build.gradle uses closures, it's case sensitive when adding dependencies