now allowing numeric identifiers to be used in 'file' annotations; more informative failure of missed cases by raising ANNOT_STRUCTURE instead of the default Match;
now allowing numeric identifiers to be used in 'file' annotations;
more informative failure of missed cases by raising ANNOT_STRUCTURE instead of the default Match;

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