Clean up docs for graphicsview.
Clean up docs for graphicsview.

Move the graphicsview snippets to qtbase/src/widgets/doc/snippets

Change-Id: Id1a65f07f4687465499fc5666bb1ad710914fabd
Reviewed-by: Casper van Donderen <808524cef5c654648bea2a2b954f3b3445ed083c@nokia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc