rename CLI switch `--outfile` --> `--output-file`

[jkowalleck]

Is your feature request related to a problem? Please describe.

there is this CLI switch outfile. the name is not quite fine.
lets use --output-file instead

Describe the solution you'd like

• rename the CLI switch outfile to output-file.
• add a "hidden" CLI outfile that is an alias for the new output-file -- this way the CLI switch is deprecated, but not removed.

Describe alternatives you've considered

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Additional context

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Contribution

• I am willing to provide an implementation
• I will wait until somebody else implements it