* gitignore for JENKINS_HOME Jenkins settings
This allows an admin to use git to keep a backup of Jenkins settings
without tracking binary artifacts. Useful for preserving settings during
plugin upgrades.
Note: secret.key is purposefully not tracked by git. This should be
backed up separately because configs may contain secrets which were
encrypted using the secret.key.
See also:
* http://jenkins-ci.org/
* https://wiki.jenkins-ci.org/display/JENKINS/Administering+Jenkins
* Add a few entries to Jenkins gitignore
