closes #440

sets minimum python version and cleans up type annotations. Unions[X, Y] -> X | Y, and builtins ex: Dict[str, list] -> dic[str, list]

move generate_add_graphic_methods.py to new scripts dir out of source tree

Unfortunately the new X | Y annotations don't show up in the add_graphic methods since the autogeneration by inspect.signature returns them in the old form with Union, ah well.