Reading, writing, arithmetic — and poop? New York education officials adopted emergency rules last week mandating that schools set a policy for taking care of young kids’ number ones and number twos — just in time for an expansion of state-funded daycare and pre-K programs . But nobody wants to be left holding the dirty diaper. The state’s new “diapering and toileting” requirement for districts has left schools scrambling for clarity over who gets to be on doody duty: teachers, teacher’s aides