Settings Model `SpecialDict` needs fixing

[benhoff]

I haven't parsed through what the original logic or reasoning behind checking to see if an item does not equal a tuple, but I'm pretty sure the logic is fundamentally broken.
See: https://github.com/benhoff/CHATIMUSMAXIMUS/blob/master/chatimusmaximus/gui/models/settings_model.py#L54

I think this check needs to be changed to see if the item is an instance of a tuple (or probably better, an iterable) and then see if it is non-empty.

Also the class name is awful.