[JENKINS-20023] Add support for java -jar jenkins-cli.jar help <cmdname>
[JENKINS-20023] Display detailed CLI command info via Jenkins UI
[JENKINS-20023] Generate usage for CLI commands registered via CLIMethod annotation
[JENKINS-20023] Restrict use of CLIAction
Merge pull request #973 from olivergondza/cli-help

[JENKINS-20023] Make CLI interface help more accesible