JOE should show the list of job chains instead of jobs when browsing through job chains in return_code configuration

Current situation
In the form on_return_code that is shown when adding on_return_code elements to a job chain node, there is a browse button for selectin the job chain to which an order should be added.
When clicking the button, only jobs are listed.
Desired behaviour
When clicking the buttons, only job chains should be listed.