SW: OST Open SAR toolkit

Install OST Open SAR toolkit

https://github.com/openforis/opensarkit

Looking at the installer for OST, we need to determine if we can install all requirements with apt (taking stretch-backports into account) and R install.packages() and extend our package-lists and the R package hook.
Major block is the installation of Orfeo Toolbox with the mosaicking tool. 