unused, uncomplicated, and very complicated

can never have worked, as output arguments are not passed by reference

minor corrections

simpler fct names; resolve Qt deprecation warnings; reformat c'tor initializer lists

except for QWheelEvent::position, not yet supported under Qt5.12

rename -> ISimulation

for consistency with other interface classes

    t = re.sub(r'(\W)(Simulation)(\W)', r'\1I\2\3', t)
    t = re.sub(r'(/)I(Simulation)', r'\1\2', t)

rm unused functions; move Bessel fcts to separate source pair