Implement a GET method for simulation's output files

[Baguage]

Moved from redmine, ticket 6366
Possible URL would refer to the simulation's output files as a collection of subordinate resources:

• GET /api/v1/simulations/1/output/

This could be used by VecNet CI to retrieve a simulation's output files if the attempt to POST them by Simulation Manager fails. It would be alternative to requesting the Simulation Manager to re-POST the files (issue #6365).