Moving towards actually using icon-naming-spec names

I don't see much progress with moving towards actual use of the icon naming spec
yet. Bug 396994 has a patch to make the .directory files in gnome-menus use
spec-compliant names where applicable. I think we should do that for 2.18.

While doing the patch, I noticed that the icon naming spec does not list
preferences
applications
settings (for the Administration menu)
documentation

as standard categories. Maybe preferences and applications are implied by
the fallback-to-generic names scheme in the spec, but they should probably
be listed explicitly, since e.g. the gnome icon theme is missing them.

Matthias