revise variable naming

Guide: https://peps.python.org/pep-0008/#naming-conventions

Try to go through all the code, and adapt variables names, to something more insightful, less confusing, etc. Some candidates are:

• avoid abbrevations (they are more difficult to decipher and have multiple spellings), prefer spelled-out names:
  Dataset.design_par --> Dataset.design_parameters
Dataset.perf_attributes --> Dataset.performance_attributes
• The whole issue with flag_norm and flag_unnorm
• in data_objects.constants
  • --> CAPS to all constants
  • fullname_dp instead of dp_long, and the other related
• in DataBlock:
  self.dobj_list_orig = dobj_list (initial input) - it is a bit confising that the self.dobj_list does not contain the dobj_list but a transformed version.
  self.dobj_list = None --> change to self.dobj_list = [], since it's going to be a list after all