update functors

doc/Pair.hs

src/Copar/Functors/AbsorbingPolynomial.hs

src/Copar/Functors/Bag.hs

src/Copar/Functors/Distribution.hs

src/Copar/Functors/GroupValued.hs

src/Copar/Functors/MonoidValued.hs

src/Copar/Functors/Polynomial.hs

src/Copar/Functors/Powerset.hs

src/Copar/Functors/SomeFunctor.hs