AIP Conference Proceedings [AIP Publishing Symmetries and Order: Algebraic Methods in Many Body Systems: A symposium in celebration of the career of Professor Francesco Iachello - Connecticut, USA (5–6 October 2018)] Symmetries and Order: Algebraic Methods in Many Body Systems: A symposium in celebration of the career of Professor Francesco Iachello - Symmetry and order in nuclear structure originating from the proton-neutron degree of freedom