Decoupled the docker image from the api

The python scripts living in the docker image are current mixed with the one used from the experimenting api. Additionaly some of them rely on the constants defined for the API part. the goal is to decoupled them and rebuild the docker image when necessary.

• Remove the use of default values in notansiv.py and adapt the api immplement accordingly (enforce the right default values there)
• Create a docker subdirectory to move all files related to the docker image inside. Adapt the .gitlab-ci.yml to build the docker image from this place.
• Rebuild the docker image only when the docker directory content is changed.