caching (similar functions)

I occured to me that there are many functions that actually do the same: caching (runs, datasets, flows, etc)

Would be good to unify these functions and get rid of many maintainability things.

Great idea! We should have a decorator to add caching to functions which only retrieve a single XML. I'm not sure whether we can actually generalize caching of datasets and tasks (the main objects) in a reasonable way.