Return total transformation instead of list of transformations

[G-nn-r]

What?

Replace the transformation_history return value of the icp()-function with transformation.
While the list of transformations might be interesting to investigate the convergence, the total transformation would be a more interesting return value for most applications.

Why?

For instance, it can be helpful when the point cloud has been created by processing a 2D image, which also might be transformed.

[shrinivas96]

I agree, the final transformation matrix is more interesting.