Introduce and use a meta file format for URLs and available versions
Fixes #21 (closed) Fixes #9 (closed) Fixes #10 (closed) Fixes #5 (closed)
Not supposed to be merged right now since it's not clear where we want to host those meta info files.
Files are currently here: https://gist.github.com/hasufell/71bf6cf0d3606d5b9a71c633940610bf