[JENKINS-10502] Option to make the build NOT fail if there is nothing to archive
fixed compilation error
Backwards compatibility added. Added allowEmptyArchive test
Added help-allowEmptyArchive.html. Did some cleanup in ArtifactArchiver and config.jelly
Merge pull request #732 from pjrt/JENKINS-10502

[FIXED JENKINS-10502] Option to make the build not fail if there is nothing to archive