support hierarchical job model (cloudbees folders)
prevent a NullPointerException when current user don't have permission to view the target item (or item has been deleted)
make autocomplete context-based
support folders within onRename
fix: onJobRenamed/onJobDeleted not invoked for jobs in folders
Added tests
(cherry-picked 830a610c7d9422889d2c276c611b1df4efecd931)
Merge remote-tracking branch 'imod/conditional-buildstep'
adapt pull request #42 to API change
Added tests for deleting projects with folders, and a test for computeRelativeNamesAfterRenaming.
ported computeRelativeNamesAfterRenaming from hudson.model.Items.
Added a test for fix of NPE in BuildInfoExporterAction.
Return a list containing null with getTriggeredBuilds if the project is deleted.
Merge pull request #45 from ikedam/feature/ItemGroupSupport

  Item Group Support (improvement of #43), including fix for JENKINS-19793 (#44)