switched to heterogeneous equality, dealt with consequences, added some equality module, proved TotEq.
	modified:   Categories.agda
	new file:   Equality.agda
	modified:   Functors.agda
	modified:   Kleisli.agda
	modified:   MaybeMonad.agda
	modified:   Monads.agda
	modified:   PartialMaybe.agda
	modified:   RestrictionCat.agda
	modified:   Sets.agda