Command line pairings

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• Expertise: ★★☆☆☆
• Time: ★★☆☆☆
• What needs to be done: Many command line options are defined pairwise, e.g. -principal and -no-principal. Currently this has to be done manually and there is no higher level way of expressing that we want to add a pair of options that negate each other and to say which one is the default. It would be good to have a way of doing and use it for the existing options where this makes sense (and ensure that all boolean options have an appropriate negating option).