added witness_sorts, univ_witness; removed nonempty_sort;
added witness_sorts, univ_witness;
removed nonempty_sort;

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