Distinguish between production and development docker images

[larribas]

As we did on the RENO project. You can basically copy it around I guess (if you decide to use Rocker), or use two different Dockerfiles.

The logic behind this is... from a purely prod environment, I don't need Node, NPM, or any of the node_modules to be installed, right? I only need the dist/ folder contents. And then, my image goes from 400MB+ to 20MB+, and so the memory footprint of the containers is lower (and we get to pay less for DigitalOcean, if we need to scale out!).