GenerateSynopsis will generate a consistent snnopysis for a top level command with N sub-commands contained within it.

GenerateUsage will return a usage string to a top level command with N sub-commands contained within it.

SetupSubpackage is a helper to create a Commander to hold the actual commands run inside of a top-level command.

HasSubpackage should be implemented by users of SetupSubpackage to help with introspecting subpackages of subcommands.

PredictArgs can optionally be implemented to help with command-line completion.