Always show icons for Create Document submenu

[Luca <elle uca libero it>]

Filed as bug #602909

Now that GNOME has switched to no-menu-icon default, to match
guidelines[1] Nautilus should enable "always show" properties for
entries in Create Document submenu.

The lack of icons here is an usability issue: there is no way to
identify the file type you are going to create, due the strip of file
name extension.


[1] documents, bookmarks, applications, and devices.