Add more information in documentation / scripts / installation

[dumprop]

Doc needs some style fixes New OS support (currently seems that this script works correctly on my ubuntu 18.04, but 20.04 - ?) 4 years ago? yeti.py fails without arguments, probably help information would be more useful Also possible features: MacOS/Yunohost/caprover installation?

[sebdraven]

Now, we'll support only docker install I think. It's more simple