serve rejected --quiet ("unexpected argument"), so there was no way to
silence the per-page WARN logs (obscura_browser::page script errors) that
flood the console when serving pages with broken scripts. Add the flag to
the Serve command and cover it in is_quiet_command, so it maps to the same
"off" log filter that fetch and scrape already use. Closes#264.
SGavrl
2e82b6c85f