Added GitLab CI.

.gitlab-ci.yml

+build-image:
+  stage: build
+
+  before_script:
+    - docker info
+    - echo $CI_REGISTRY_IMAGE
+    - echo $CI_COMMIT_REF_NAME
+    - echo -n $CI_JOB_TOKEN | docker login -u gitlab-ci-token --password-stdin $CI_REGISTRY
+
+  script:
+    - mvn -T 4 clean install
+    - cd dockerfiles && ./build.sh --tag:$CI_COMMIT_REF_NAME --organization:$CI_REGISTRY_IMAGE --skip-tests && cd ..
+    - docker push ${CI_REGISTRY_IMAGE}/che:${CI_COMMIT_REF_NAME}
+    - docker push ${CI_REGISTRY_IMAGE}/che-postgres:${CI_COMMIT_REF_NAME}
+    - docker push ${CI_REGISTRY_IMAGE}/che-keycloak:${CI_COMMIT_REF_NAME}
+
+  tags:
+    - shell