Description

This MR will allow using the PSolver library also in sequential runs, as well as using the sequential PSolver library for a given MPI task.

News snippet

Remove dependency of using the PSolver library on MPI

Checklist

I have checked that my code follows the Octopus coding standards
I have added tests for all the new features added in this request.

Closes #282 (closed)

Edited Jul 13, 2020 by Martin Lueders