A commit that's just too big.

Too many changes in one commit that aren't relevant to each other all
because I didn't commit these for some time and they piled up, exactly
what I shouldn't do.

- Remove some Git submodules. They're not needed.
- Remove the REPREPRO_BASE_DIR environment variable, it's set with
direnv inside that project.
- Use Docker Buildkit.
- Use auto Python interpeter with Ansible, prefer Python3.
- Better ls aliases.
- Netcat aliases to listen and check ports and sockets.
- Aliases and functions for Terraform.
- Use Black to format Python code.
- Show the run duration and exit code in a line before the prompt, maybe
better with Bash earlier than 5.0, where there's an annoying with line
wrapping.
- Valid name for the flatpak_kill shell function.
- Delete user-dirs files, didn't do anything anyway.
- Convert README from reStructuredText to Markdown.
- Don't install gsutil with Python2, use snap to install the Google SDK.
- More pre-commit hooks, update the exiting ones, format the file for
yamllint, Use flake8 from it's repo, the one from the hooks repo is
deprecated.
- Clean the Shore SSH config.
- Add the shared AWS keys to the Endless SSH config.