This fixes the following bugs:
o copy of shapes with a pattern backgound run into an assert
o make copy and paste of images and objects with pattern background work
o fix bug in WMFImportParser to use the image collection correctly.
  The image collection was not found
o make it possible to add also remote images e.g. over fish://
o make copy and paste of pages with background images work in kpresenter
  and kivio

Also done
o make sure that if the same picture is added more then once to use the
  same data for it
o added first unit tests for KoImageCollection
o use the shape saving context to store the images which need to go into
  the saved store.
o don't stop loading if e.g. a image can not be loaded.

I hope I did not break anythink. As far as I can see all works well.
The karbon filters should be tested to see if it is all working as
expected.

I also disabled the code in the shapeselector to show the clipboard as
it crashes as soon you twice copy a picture.

svn path=/trunk/koffice/; revision=871587