Adapt the <only> syntax to branch@organisation/repo according to https://docs.gitlab.com/ee/ci/yaml/#onlyexcept-basic

Remove debugging ls. Activate double accuracy for the numerical tests. Deactivate 256 & 512 grid sizes.

Add gpu options to root cmake. Add the cmake option for passing the path to the numerial tests. Add git clone test to the CI.

Set jobs to manual, as long the gitz gitlab has no windows runner and sonarqube is not transferred to one of the runners.