Add artifact classifier to ChangeRocorderXML

[ggkochanski]

When two dependencies differ by the classifier only then they appear twice in file version-changes.xml but you cannot distinguish which is which.

The general idea is to add the artifact's classifier attribute to node /updates/dependencyUpdate when is set:

        DependencyVersionChange change = (DependencyVersionChange) changeRecord.getVersionChange();
        update.setAttribute("groupId", change.getGroupId());
        update.setAttribute("artifactId", change.getArtifactId());
        if(change.getClassifier() != null) {
            update.setAttribute("classifier", change.getClassifier());
        }