Whittaker-Henderson smoother

For a project regarding satellite images and interpolating measurement values, it was necessary to use a Whittaker-Henderson smoother for first-order and second-order differences.
Since the development was done in Julia, there was not such a smoother and interpolation algorithm available and, therefore, it has been written by us.

The package is officially published in Julia's metadata repository and can be easily installed and used by all Julia users.

You can find the source code and a short documentation on its GitHub page: https://github.com/muhlba91/Whittaker.jl