DOAP files: core,core-apps,apps categories (=moduleset)

[Olav Vitters <olav vitters nl>]

In a given doap file, there is an item defining the category:
  <category rdf:resource="http://api.gnome.org/doap-extensions#desktop"; />

I've added:
 - core
 - core-apps
 - apps

The following are not allowed anymore in changed doap files:
 - admin
 - bindings
 - desktop
 - development
 - platform
 - productivity

TODO:
 - Change category in a bunch of modules
 - Properly announce this change
 - Update documentation

-- 
Regards,
Olav