Investigate options to generate a Multi-Release JAR

[mrotteveel]

We're currently creating separate artifacts per Java version. Creating a Multi-Release JAR might allow us to reduce to a single artifact. Investigate the possibilities and limitations.

See also: https://blog.gradle.org/mrjars

Possible things to explore:

• Testing (e.g. for features only in the Java XX, but not in the baseline, existing example would be the ChaCha encryption plugin)
• Java Module System