Programmatic way of updating JSON summary instances

[seba-1511]

Since you can fetch a JSON summary, you should be able to modify some of its values, and either call .save() which creates a new result, or call .update() which modifies the result. Probably also a good idea to have .delete() for removal of results.

[seba-1511]

I am not sure if this is really a good idea in the end. It feels like once results are saved, they should never be modified since they are the most representative of the "raw" data. Instead, it might be more useful to clone/copy them into another experiment's directory.