Support for JobDSL specific dependencies

[pvdissel]

Currently, to be able to use JobDSL plugin specific classes in the jobdsl script with auto-completion et.al., you need to add those to the project dependencies in gradle making them available to IDEs. This is cumbersome and not wanted.. jobdsl dependencies should not be part of the real code project.

Can we add an additional gradle configuration which is not used by any of the code project sourcesets, but only help IDEs providing auto-completion