By not providing specific examples, we reduce the maintenance effort I
believe. I didn't want to add examples for all tljh-config commands as
those were anyhow documented via --help, and it felt like too much
documentation to maintain to describe it better than that.
Removes a lot of 'sudo -E' usage, and eventually should
let us get rid of the $PATH override for jupyterhub-admins,
which arguably is less secure than just dropping stuff into
/usr/bin
Also remove sudo -E from apt and mkdir calls. Not necessary.
