build classes/arities: refer to operations in sorts.ML; simplified add_class/classrel/arity; tuned;
build classes/arities: refer to operations in sorts.ML;
simplified add_class/classrel/arity;
tuned;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle