In POM files, configured "maven-assembly-plugin" to avoid build warnings and...

In POM files, configured "maven-assembly-plugin" to avoid build warnings and renamed final JAR files.

.gitlab-ci.yml:
- Use new JAR names when packaging via "python3 -m zipfile".

VadereGui/pom.xml:
- Renamed JAR from "vadere" to "vadere-gu".
- Renamed JAR from "postvis" to "vadere-postvis".