Provide Gradle sample projects

[dennisfischer]

Currently there are no working example projects which use Gradle. The documentation states that Gradle can be used. However, none of the existing samples showcases how development with Gradle does work.

There are a few options that can be considered:

• Have a dedicated sample for Gradle
• Have a Gradle configuration alongside the existing Maven configuration for some / all samples
• Provide sufficient documentation to get started with Gradle without a sample project

[jmrodri]

We could add a Gradle build file to one of our samples to satisfy this issue.