Dockerize backend and frontend

[debuglevel]

Both backend and frontend should be built and deployable from a docker container

• [x] rest: build docker image
• [ ] rest: integrate into gitlab-ci
• [x] planner: build docker image
• [ ] planner: integrate into gitlab-ci
• [x] Angular: build docker image
• [ ] Angular: integrate into gitlab-ci
• [x] Angular: get backend URL from environment