Added ".gitlab-ci.yml" with first target "unit_tests_with_coverage".

.gitlab-ci.yml

+unit_tests_with_coverage:
+  # A job is always executed within a stage.
+  # If no stage is set, it defaults to 'test'.
+  stage: test
+  
+  # Here you can execute arbitrate terminal commands.
+  # If any of the commands returns a non zero exit code the job fails.
+  script:
+    - mvn test
+    
\ No newline at end of file