Self-merging a few smaller PRs - issue for visibility and retroactive feedback

[consideRatio]

I've went for a few self-merges of smaller PRs like these that I think may be fine to merge, in order to retain momentum and not become blocked to contribute further in this repo.

Self-merged PRs

• Add some docstrings and inline comments #121
• Error in build_dashboard if about to return empty object #122
• Fail loudly if GRAFANA_TOKEN or jsonnet isn't available #124
• Make ensure_folder function also update an outdated folder title #126