Clarify use of Dockerfile and add/update build steps

[limond]

The current development process consists of starting the services defined in dev/docker-compose.yml which will give you

• an auto-refreshing Github Pages (Jekyll) server
• an auto-refreshing grunt service for asset generation

At the root of this project exists a Dockerfile which builds and serves the site from an nginx server. I neglected this file until now since the nginx server depends on a reachable host "frost" and uses certbot for TLS certificates. For development purposes and while hosting the site via Github pages it was neither necessary to have a local frost server nor to generate TLS certificates.

If there is a need to run this webpage locally (as a non-development deployment) and move away from gh-pages, there should be some changes to the Dockerfile:

• Update Github pages version (at least to version used in the development service, better update both to latest)
• Maybe: generate grunt assets as a build stage (The only reason generated assets are currently available without building is that they are checked in because of github-pages)

Also there is a conflict when using the development services in dev/docker-compose.yml and building the root Dockerfile as the former generates a conflicting Gemfile.lock

[suniastar]

I am not very familiar with this project but the Dockerfile was required by the smartaqnet-infrastructure project. As part of the new smartaqnet infrastructure I would try to remove this Dockerfile from its dependencies.