[knewfilemenu] Write Name when creating Link files

When creating a desktop file for a link we use the link label as file name and sometimes append .desktop

Folderview will show the name including the .desktop suffix, which isn't very nice.

Folder view/the desktop kio slave has special code to render a better name for desktop file using the Name entry in the desktop file

Set this entry when creating the desktop file to make use of it