Sorting by multiple attributes

Hello,

I created to made possible sorting by multiple attributes.

I want achieve "natural file orders" ie. folders alphabetically, next to files alphabetically. So first folders, next to other files.

I removed "Schwartzian transform". Reffering to https://wiki.python.org/moin/HowTo/Sorting there is no reason to do this kind of idioms in Python since 2.4 version.

Unfortunately, I don't know how to separate others commits from my forks. I am sorry.

Greetings,
Adam Dobrawy