Merge branch 'feature/portable-ci' into 'master'

[ci] Make .gitlab-ci.yml portable

See merge request !1482

.gitlab-ci.yml

@@ -3,12 +3,8 @@
 
 ---
 include:
-  - project: 'core/ci-config'
-    ref: master
-    file: 'config/common/master.yml'
-  - project: 'core/ci-config'
-    ref: master
-    file: 'jobs/common/master.yml'
+  - remote: 'https://gitlab.dune-project.org/core/ci-config/raw/master/config/common/master.yml'
+  - remote: 'https://gitlab.dune-project.org/core/ci-config/raw/master/jobs/common/master.yml'
 
 before_script:
   - . /duneci/bin/duneci-init-job