Merge feat/kubernetes-integration into develop

See merge request teraflow-h2020/controller!15

Skeleton of "compute" service.

See merge request teraflow-h2020/controller!13

Update the gitlab-ci.yml_generator.py file

Added python script to automatically generate a gitlab-ci.yml file

Integration of Service service, multiple improvements in Context and Device services, and GitLab CI pipeline integration and functional tests

See merge request teraflow-h2020/controller!12

Common / Context / Device / Service:
- Improvements in unitary testing
- Extended assertion validators tor testing
- Factorized service implementation code to improve testability, reusability and increase code coverage

Factorization of code between services and minor unitary testing improvements. (Not finished, it is just a backup)