Fix Gitlab-CI (#441)

* Added Job-Token as needed by Gitlab

* Moved schedule towards nighttime

and triggered CI again, as HPC-Systems are now back

* Schedule gitlab-ci workflow at the same time as github-workflow

* Moved installation of more packages into preparation to avoid parallel access of files

* First try to use virtual envs from python

So that installed packages are available in later CI-Jobs

* Store venv on scratch

* Activate project to use SCRATCH

* Wrong usage of variables

* Try installing mpi4py-fft for later usage