JobSchedulers jetty plugin should handle security settings similiar the security element

Working with its internal HTTP server JobScheduler can restrict the allowed commands by setting a security level assigned to a hostname (see allowed_host element).

The goal is to adapt the use of security levels for user authorization via Jetty. This means that it should be possible to assign a specific user to a user group that restricts the execution of JobScheduler commands (analogous to the level attribute).

Different security levels at host level should not supported anymore via Jetty.