Move $HOME env variable outside web server's Document root

[SlouchyButton]

Overwrite $HOME env variable for all supported versions. Default $HOME is directed inside the web server's Document root, which means that applications that save potentially private data to $HOME (e.g. bash's histfile) will save them into a folder accessible outside the container via the web server. This means there is a possibility of leaking the data.

This does not occur in all cases, namely bash won't create a histfile at all, when user sets a different user via --user= argument in podman run command, as in that case bash doesn't have a permission to write into the $HOME.

Fixes: #255