Don't only consider jenkins root jobs as eligile parents

when jobs are organized into ItemGroups (cloudbees folders plugin) clone workspace don't show them as eligible parent as it only consider Hudson.instance.items vs "allItems"
Use full name for jobs
when jobs are organized into ItemGroups (cloudbees folders plugin) they need to be retreived using fullname.
Don't use display name, that may not be resolved later by getItemByFullName
resolve conflict in CloneWorkspace.