klipper: additional options
klipper: additional options

This allows for easier interop with Moonraker, as well as giving an
ability to store klipper configuration files in /var/lib/klipper, thus not
littering /etc with all the backups SAVE_CONFIG does.

- Added `configFile` as an alternative way to specify configuration
- Added `isMutableConfig` and `mutableConfigPath`

Co-authored-by: @lovesegfault <9c4123796a4a87b44fd25dd7025e8bb21ebf56fe@meurer.org>
Co-authored-by: Sandro <3f1bc63e633623a49b6f9d32f242d8ac8d282b0e@gmail.com>
Co-authored-by: Bernardo Meurer <9c4123796a4a87b44fd25dd7025e8bb21ebf56fe@meurer.org>

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