build.gradle to publish both sources and javadoc

[gb96]

Current gradle build only publishes compiled Java classes to maven repository.

It helps java developers if sources and javadoc are also published as most Java IDEs can leverage those to provide better assistance (particularly during run-time debugging, static code analysis, and also for developers learning new api).

I realise there is currently little or no javadoc tags in the generated java sources, however in future it might be possible for genjava to include some additional information via those tags.

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[jubeira]

Hi @gb96, thanks for the PR.

Please correct me if I'm mistaken, but genjava is mainly used to generate the artifacts for messages and services. Is that the documentation you would like to have in the JAR files?

That being said, I think it could be a good improvement; we should cherrypick the changes to Kinetic as well. @drigz any thoughts?

[drigz]

No comments from my side - I haven't been using the Gradle build much.