Upgrade to Java 8 LTS and optional module-info

[claussni]

Since the library is small and does rely on modern Java features by design, it might be helpful to upgrade to Java 8 LTS in order to support older runtimes as long as possible.

Additionally the Java Module System used with newer runtimes would benefit from a module-info definition to avoid generation of overly broad automatic modules. A multi-release JAR could be used for that.

• JDK EOL
• JEP 238: Multi-Release JAR Files
• Older projects with module-info