first-class support for subcommands

[HeladoDeBrownie]

although there can be many usage strings for a given command, they are all required to route to the same run function. for commands with a large number of usages, it can be confusing to separate out all the cases, which are in practice going to be handled by an if statement regardless, even if they have some shared logic. this can be handled better. try designing it so that each usage can route to its own function