[packagekit] PackageKit Collections.

[Tim Lauridsen]

He had a little discussion on irc today, about how to support yum groups 
   and other similar type of groups in other backend types.

The idea was to handle the yum groups as metapackages shown in the gui 
in a special 'Collections' group.

if you select the Collection you will see all yum comps groups as 
metapackages there can be install/removed/updated.

In the api installPackages etc are extended to handle meta packages

ä meta package id is just like an normal package id but with a special 
keyword instead of a repoid. it could be [meta] or ~meta.

if a backend dont support this then it just dont return any members for 
the collection group (GROUP_META_PACKAGES).

Let me know what you all thinks.

Tim