Installer should use not hard code the drools/jbpm versions, but instead use the maven properties ${drools.version} and ${jbpm.version}

The currently linked Drools Installer (http://download.jboss.org/drools/release/5.1.1.34858.FINAL/drools-5.1.1-install.zip) does not work with the contacted Repository at https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/ as there's no longer drools-5.1.1.* files rather than 5.2.0 SNAPSHOT Files.