export the lib behind the widget explorer

[Giulio Camuffo]

Hi,

The widget explorer and the activity switcher are sharing a lib providing some 
convenience classes that allows them to easily share the appearance.
This lib is located in kdebase/workspace/libs/plasmagenericshell and it is not 
exported.
Since I'd like to provide a similar widget to add groups in my groupingdesktop 
i'm asking if it could be exported, maybe without having to maintain binary 
compatibility.
If it needs to be cleaned a bit i could do the work.

Giulio