Tests

Add some tests to this repository:

• hadolint for Dockerfiles
• shellcheck for bash and sh scripts
• yamllint for YAML files

Currently marking every job with allow_failure: yes, but if this is accepted, I guess the next step would be to fix the "problems" and remove those lines.

.gitlab-ci.yml

@@ -20,4 +20,3 @@ dockerfiles:
 yamllint:
   image: sdesbure/yamllint
   script: "yamllint $(find . \\( -name '*.yml' -o -name '*.yaml' \\))"
-  allow_failure: yes