Refactor

Update the master branch to provide a working CI again and small changes since last merge from branch 'refactor'

.gitlab-ci.yml

@@ -32,7 +32,7 @@ badges:
 
 build-mpi-nofortran-gcc8:
     stage: build
-    image: gitlab.version.fz-juelich.de:5555/slms/loadbalancing/mpich-gcc9
+    image: gitlab.version.fz-juelich.de:5555/slms/loadbalancing/mpich-gcc8
     tags:
         - public-docker
     when: always