Taking advantage of APIs available with newer Jenkins cores.
· [JENKINS-18224] TransientActionFactory simplifies adding the Move action and makes it available more broadly.
  Can therefore deprecate TransientFolderActionFactory.
· Expanding the search index to look for jobs in subfolders (matches #848 in Jenkins root).
· testReloadJenkinsAndFindBuildInProgress can now pass unconditionally.
· ListView.setIncludeRegex avoids the need for reflection.
· f:bottomButtonBar convenient in Jelly.
As yet unimplemented:
· AutoCompletionCandidates.ofJobNames could be used, though it does not filter by permitted children.
  (Nor, generally, should it, since this method is typically used for *existing* items, which might violate this restriction.)
  Might be feasible to call ofJobNames and then filter the result; or perhaps this method should accept an Item filter.