Mirror repository with Gitlab-Repo so that CI can use HPC-Resources.
This is helpful e.g. for running GPU-Tests and/or for running Benchmarks.

Tasks that should be done:

• Mirror with Gitlab for new pushes
• Mirror also for updated Pull-Requests (only if certain tags are set and people with appropriate permissions triggered CI)
• Run tests on HPC (e.g. GPU-Tests)
• Get back Reports (e.g. coverage) from Gitlab and include in Github-Statistics