First implementation of continuous integration

In this merge request a first implementation of continuous integration is proposed.

This includes the following:

• use Gitlab runner on EVE (there can be multiple runners registered)
• at the moment only the GNU compiler is used
• cmake compilation is checked with simple run of test domain
• check scripts are run for:
  • debug/release
  • sequential/parallel

Some CI related scripts were added in a new folder called CI-scripts and the configuration file for the gitlab-runner called .gitlab-ci.yml was added to the base folder.

You can add a gitlab-runner to your own fork following this instruction:

• https://wiki.ufz.de/eve/index.php/Gitlab_Runner

But you have to enable custom build dir by adding enabled = true to [runners.custom_build_dir] in the gitlab-runner config file (usually under .gitlab-runner/config.toml in your home dir on EVE).

Example:

[[runners]]
  name = "frontend1 muellese"
  url = "https://git.ufz.de"
  token = ...
  executor = "shell"
  [runners.custom_build_dir]
    enabled = true
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]