- Use *appstream* as key in one of the items for the package-
chooser to load data from the AppStream cache in the system.
- Usable for some applications; for DE-selection not so much.
- Currently unimplemented.
- Using id's as keys in a map orders them indeterminately -- in
practice, alphabetically by key. Switch to a list form so that
the products stick to the order they have in the config file
(which means distro's can list "preferred" versions at top).