Provide Import/export functionality for Job Streams from the API

Current Situation

• The Job Streams view offers the functionality to export/import a job stream in JSON format.
• However, this function is available from the GUI only as there is no corresponding API resource.

Desired Behavior

• The functionality should be moved to the REST Web Service to allow both use by the GUI and use by 3rd parties based on the API.
• The functionality should be available from the API and should be documented with the API.