Making Monofunctor and Monofoldable superclasses of Functor and Foldable

I think that mono-traversable doesn’t get enough love; it is in roughly the same position that Semigroup was in, before the Monoid hierarchy was corrected, or more recently, Functor and Bifunctor themselves. I am suggesting that we do the same hierarchy unification / cleanup with Monofunctor, and make it a superclass of Functor. My justification is that every functor is capable of performing all of the functions of a monomorphic functor, simply by not changing the element type during map. My un...