Add Maven enforcer plugin to validate JDK and Maven versions.
Introduce the Maven enforcer plugin to the POM to validate the JDK and Maven versions. Maven version should be >= 3.8.1 (nearly a year old now), JDK 1.8.0-x. We'll need to see how the JDK versions hold up across distributions and OSes. On my Mac and Ubuntu VM Zulu JDK 8 passes fine.
Edited by Moed, Matthijs
