XD-1014 + XD-1013 Show XML Config File Contents

XD-1013 Add additional REST endpoint that return the XML definition of a job
XD-1014 Command to show the XML of the job definition

Code Review Changes

* change rest endpoint url to `modules/{type}/{name}/definition`
* change MediaType to `application/xml`
* shell UI improvements
* polish exception handling

On Merge:
* Simplify client code
* Change exception type when not found