Refactor dockerfiles to use environment/readme files from context

Currently, conda/pip environment/packages are specified in the (dockerfile) recipe. As well as README file and bash-rc script(s).

Use environment/readme/sh files instead. And `COPY` them into the build context.

In particular, regarding README (to expand any variable in the template): https://stackoverflow.com/questions/10683349/forcing-bash-to-expand-variables-in-a-string-loaded-from-a-file
