replaced obsolete ProofHistory by ProofNode (backtracking only);
replaced obsolete ProofHistory by ProofNode (backtracking only);

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