Endpoint to list only locally loaded plans

[stan-dot]

To differentiate the fast iterative experiments from the well-tested ones

Would need to have more than 1 way to store the plans and devices, or a tag to browse by the origin.

acceptance criteria

• by going to /local_devices and /local_plans I can see only the locally loaded devices and plans respectively

[callumforrester]

I can see a way to tag plans being generally useful, then it can be left to the user to tag stuff as "experimental", "production" etc. as they see fit