Netdata to keep previous stable versions


We are using Netdata to power a mission and safety critical system (automated public vehicles) where updates are relatively scarse, well tested and documented. The older stable packages getting deleted on public archives is a huge problem.

This choice to delete old packages leads to users like us to implement a mirror server to mirror old releases and use our own custom package repositories. Huge hustle.
This feature also helps us to replicate errors on new versions and compare them to easily switchable old versions.

I have also created a GitHub issue about the subject as it can easily be solved with a PR.