k-means and image inpainting wrappers

[valillon]

Wrapping k-means for unsupervised color clustering.

I don't know why the opencv's k-means implementation returns properly classified segments, but the cluster centroids look odd. In this example I had to ignored the opencv centroids and recalculating them in a different way.

Two clustering samples of color and grayscale clustering created with this commit on a RGB image and its depth-map, respectively.

[valillon]

I'm adding a second wrapper for simple image inpainting, currently configured for the Navier-Strokes method with radius 3. See an example here.

Sorry for both commits in the same pull request.