Add Gitlab-CI job to check copyright

.gitlab-ci.yml

+###############################################################################
+# (c) Copyright 2019 CERN for the benefit of the LHCb Collaboration           #
+#                                                                             #
+# This software is distributed under the terms of the GNU General Public      #
+# Licence version 3 (GPL Version 3), copied verbatim in the file "COPYING".   #
+#                                                                             #
+# In applying this licence, CERN does not waive the privileges and immunities #
+# granted to it by virtue of its status as an Intergovernmental Organization  #
+# or submit itself to any jurisdiction.                                       #
+###############################################################################
+check-copyright:
+  image: gitlab-registry.cern.ch/ci-tools/ci-worker:cc7
+  script:
+    - curl -o check_copyright.py "https://gitlab.cern.ch/lhcb-core/LbDevTools/raw/master/LbDevTools/CopyrightCheck.py?inline=false"
+    - python check_copyright.py origin/2018-patches