Change URL to test server
Use introspection to overcome API differences in Google Guava

Guava changes the API in a bad way in version 15. Geppetto must
be compatible with older versions when coexisting with Xtext. It
must be compatible with recent versions to be able to run in
newer versions of the Jenkins server.
Use project.version instead of parent.version due to release plug-in limitation
[maven-release-plugin] prepare release parent-4.1.0
[maven-release-plugin] prepare for next development iteration
Add 'tags', 'requirements' and 'operatingystem_support' to Metadata entity