Add gitlab CI configuration

.gitlab-ci.yml

+stages:
+  - start
+  - build
+  - test
+
+
+build-start:
+  image: registry.gitlab.com/finestructure/pipeline-trigger
+  stage: start
+  script:
+    - trigger -h gitlab.cern.ch -a "$API_TOKEN" -p "$CI_JOB_TOKEN" -t dev -e SOURCE_REPO=$CI_REPOSITORY_URL -e JALIEN_ROOT_BRANCH=$CI_COMMIT_REF_NAME 46440