auto3dseg.DataAnalyser improvements:

• it should run on GPU by default. Current implementation always runs on CPU, without any options to change it
• histogram stats needs reworking. The default should not be -500..500 intensity range (which is very specific for certain CT data). there should be a better logic, if this range is not provided.
  As a workaround - if it is not provided, we can skip this stat completely.
• when running on GPU we should use parallel workers of DataLoader (currently it's not in parallel).
• connected components. I think we can have this option as False by default to speed up data analysis