fixes #61, preparing updatewallpaper to be moved

--update wallpaper will go to the workareas data engine. I found
that wallpapers for normal activities can be found with out issues
without using containment(). For the add new activity through
the data engine there is no problem. For the "clone activity" the
only thing that has to be made is to disable the updatewallpaper
mechanism... :) In the new activity the background is the same
with the old one from which was copied... :)
update wallpapers in now ready for the dataengine

--cloning support could also move to the dataengine but
the signal that triggers the progress dialog can not be
used that way. At the same time I think it could be
better to hide a bit the clonning support because it is not
the best of the implementations...