[FIXED JENKINS-24512] Folder support. Now targets Jenkins 1.480.3.
[FIXED JENKINS-24515] Now uses ModifiableTopLevelItemGroup, which allows free from cloudbees-folder plugin.
[JENKINS-24515] Added tests for folder support.
[JENKINS-24515] Allow copy folders.
Merge pull request #2 from ikedam/feature/JENKINS-24515_TargetFolder

[JENKINS-24515] Folder support