added type 'a parser, simplified signature; added internal_command wrapper; tuned;
added type 'a parser, simplified signature;
added internal_command wrapper;
tuned;

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