Add tests

Method getComputers() does not return computers for label expressions.

Use -Djava.awt.headless=true on Debian service

I installed the Jenkins Debian package, and later installed an XServer (XVFB).  The graphs of test results etc. were replaced by an image suggesting that I add this flag to the JVM commandline.  I don't see any reason why this shouldn't always be present on Debian systems.

purged some messages that are obsolete since
06514d25
localized redirect message

[FIXED JENKINS-18694] Generalizing fix of JENKINS-18678 to include also rename of parent folders, taking advantage of JENKINS-18028 API.

[JENKINS-18224] Relaxing type parameter restriction on TransientActionFactory since useful mixin interfaces like Item do not extend Actionable.

[JENKINS-18224] TransientActionFactory

[FIX JENKINS-21303] There is a NPE here that can and does happen for real when an aggresive slave retention strategy interacts with post build triggers that want to do token macro expansion

[JENKINS-18224] Introduced Actionable.replaceAction, allowing getActions() to be deprecated except for subclasses.

Better for SecurityListener.authenticated to take a UserDetails, since some implementations (as for AD) may have additional information.

[FIXED JENKINS-20008] [FIXED JENKINS-18028] [FIXED JENKINS-18680] #1069: support for moving jobs into or out of folders.