add option to `reproduce_analysis()` to deploy processing to Docker container

[januz]

• [x] get general Docker problems sorted out (see [here])(https://github.com/HenrikBengtsson/future/issues/265) and here
• [x] look into how to share directory between host and container
• [ ] implement check whether code is run within Docker container
  • [ ] either just check whether in a Docker container
  • [ ] or better check whether run in the right Docker container (e.g., by copying Dockerfile into container during build process and then comparing that file during execution; potentially provide Dockerfile in inst/)

[januz]

instead of providing Dockerfile in container, download it from GitHub/GitLab using the respective "raw" URL with curl:

• GitHub: https://raw.githubusercontent.com/<user>/<repo>/master/Dockerfile
• GitLab: https://gitlab.com/<user>/<repo>/raw/master/Dockerfile

Then compare md5 checksum with file that is saved in container.

So...

1. check whether in Docker container
   • if not, warn user and suggest running workflow through Docker
2. compare md5 checksums
   • if they don't match, warn user