Updating Refinement classes

[dario-coscia]

Is your feature request related to a problem? Please describe.
The refinement classes at the moment are not working, the DataModule/Dataset needs to be updated to handle varying points during training.

[dario-coscia]

Related to #481

[dario-coscia]

Hi @FilippoOlivo ! Are you working on this and #481 as well? I see that you inserted 16th May as the deadline, just put me in review once done. In case you need help, open a draft PR and I'll see if I can help