Display version number of Internet.nl code in frontend

[baknu]

Display version number of Internet.nl code in frontend, e.g. in footer.

[gthess]

As discussed during a meeting this could reflect the latest tag release (e.g., v1.3.2).
This would make sense only if all the live versions are done by checking out version tags.

If a version needs to go live that is not yet part of a full release (e.g., updating straight from the master branch), or different development versions are live, then using the git commit hash would be easier to understand.

This could be integrated in the make translations command (necessary while deploying) to get the version string from git and replace it in the translations/*/main.po files before generating the django files. That would mean that a distinct place holder needs to be in those files for a trivial text replace logic.
git describe --tags and git rev-parse --short HEAD could prove useful to getting the version string.

Then optionally the displayed version could be a link to <github_address>/Internet.nl/blob/<tag or commit hash>/Changelog.md.