moved certify_class/sort to type.ML; added operations to build sort algebras (from type.ML); tuned;
moved certify_class/sort to type.ML;
added operations to build sort algebras (from type.ML);
tuned;

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