Added a general refutation tactic which works by putting things into nnf first.
Added a general refutation tactic which works by putting things into nnf first.

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