feat(docker, front): cleaner & more reproducible frontend

• The frontend dependencies are now cached in the docker images itself
• A little hack is used to restore them when needed ie: the node_modules folder is stored outside of the workdir and then brought in
• Images are now versioned on the registry
• The docker-compose file has been updated to use the new/versioned images.
• The documentation has been updated.
• And the Gitlab-CI has been tweaked.