Fixed the 'new style getargs format' error in Entity property setters by:
- Implementing PyObject_to_sfVector2f/2i using PyVector::from_arg
- Adding proper error checking in Entity::set_position
- Implementing PyVector get_member/set_member for x/y properties
- Fixing PyVector::from_arg to handle non-tuple arguments correctly
Now Entity.pos and Entity.sprite_number setters work correctly with
proper type validation.
