New possibility to embed 2D images in Viewer3D

In association to the  Point2DEmbedderIn3D, it now allows to display images with a direct embedding:
 DGtal::Point2DEmbedderIn3D<DGtal::Z3i::Domain >  embedder(...),
 ImageAdapterExtractor extractedImage(imageVol, domainImage2D, embedder, idV);

viewer << extractedImage;
viewer << DGtal::UpdateImage3DEmbedding<Z3i::Space, Z3i::KSpace>(pos, 
                                                                     embedder(Z2i::RealPoint(0,0)),
                                                                     embedder(Z2i::RealPoint(IMAGE_PATCH_WIDTH,0)),
                                                                     embedder(domainImage2D.upperBound()),
                                                                     embedder(Z2i::RealPoint(0, IMAGE_PATCH_WIDTH)));
And then you could have such example visu:
![capture decran 2013-11-18 a 16 50 26](https://f.cloud.github.com/assets/772865/1564257/cc037b54-506c-11e3-91bf-c9dc7027ab9d.png)