major cleanup and reorganisation; added generic_extend, generic_merge; added various minor functions;
major cleanup and reorganisation;
added generic_extend, generic_merge;
added various minor functions;

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