removed rev_append; tuned presentation of datatype option: removed apsome, export the and if_none;
removed rev_append;
tuned presentation of datatype option: removed apsome, export the and if_none;

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