Interface YargCommand

Combine the tree of commands, convert duplicates into warnings. After this, you should only save.

This exists to be compatible with yargs syntax once we aren't using it, we could remove it

This exists to be compatible with yargs syntax But really, we'll figure out whether to call demandCommand() on yargs based on whether a handler function was supplied

This exists to be compatible with yargs syntax once we aren't using it, we could remove it

Add a subcommand. Pass in a yargs-style object, except you can also include conflictResolution and Parameters