add --clean option

[jdotbdot]

This command line option gives a clean Node-red and Node.js installation the same as a first time install.
All non-core nodes installed, flows, settings.js and other customisations are removed.

• Give warning about deleting .node-red directory.
• Stop Node-red.
• Set FORCE_NODE="y" to reinstall the default node.js. (unless overridden by eg --node22)
• Delete the .node-red directory, thus removing installed nodes, existing flows, settings file & other customisation.
• Install default Node-red version. (unless overridden by eg --nodered-version=4.1.1)
• Replace systemd script with the current default.
• Run admin init script. (unless overridden by --no-init)
• Do not restart Node-red - though if systemd script is enabled it remains enabled.

[linux-foundation-easycla]

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• ✅ login: jdotbdot / name: jdotbdot (a37bf5a)