Turns on "natural" sorting for the document list in the filetree addon,
so that e.g. 10 comes after 9, not before.
That's how the KDE4 version behaved too.
That's how the KDE4 version behaved too.BUG: 375676
As this is a simple fix, I'd like to commit it to the 17.04 branch too if there are no objections.