Elastisys root pom. Specializations need to specify a ${docker.registry} property for the targeted docker registry (e.g. 'index.docker.io/v1/' or 'my.private.registry:5000') and may want to specify a template for the ${docker.registry}/elastisys/elastisys-pom-root property (such as '${docker.registry}/elastisys/elastisys-pom-root' for a private registry or just 'elastisys/elastisys-pom-root' when using docker hub).