Ci

Created two github actions: The build-src and the build-doc. The names are self explaining. Build-src contains the build stages for all cim_versions. build-doc contains creates the documentations for all cim_versions and uploads them as artifacts. Due to the fact, that Github does not support hidden keys and anchors yet, we can not use the nice templating scheme from gitlab-ci.yml but instead need to copy&paste the code for each cim_version.