cli: Add setup and firstboot commands

This adds two new top-level commands: setup and firstboot.

Firstboot is pure-golang implementation of a service that runs some
commands once when a system first boots. You need to install this
service, and put the scripts to run in a special directory. This is
inspired by the virt-builder --firstboot mechanism.

Setup is a general purpose command that makes it easy to setup certain
facilities on a new machine. These include the mgmt package dependencies
it might need, a service to run it from, and the necessary service to
use the mgmt firstboot service as well.

All of this has been built to facilitate handoff between provisioning a
new machine and running configuration management on it.

cli/cli.go

@@ -119,6 +119,10 @@ type Args struct {
 
 	DeployCmd *DeployArgs `arg:"subcommand:deploy" help:"deploy code into a cluster"`
 
+	SetupCmd *SetupArgs `arg:"subcommand:setup" help:"setup some bootstrapping tasks"`
+
+	FirstbootCmd *FirstbootArgs `arg:"subcommand:firstboot" help:"run some tasks on first boot"`
+
 	// This never runs, it gets preempted in the real main() function.
 	// XXX: Can we do it nicely with the new arg parser? can it ignore all args?
 	EtcdCmd *EtcdArgs `arg:"subcommand:etcd" help:"run standalone etcd"`
@@ -155,6 +159,14 @@ func (obj *Args) Run(ctx context.Context, data *cliUtil.Data) (bool, error) {
 		return cmd.Run(ctx, data)
 	}
 
+	if cmd := obj.SetupCmd; cmd != nil {
+		return cmd.Run(ctx, data)
+	}
+
+	if cmd := obj.FirstbootCmd; cmd != nil {
+		return cmd.Run(ctx, data)
+	}
+
 	// NOTE: we could return true, fmt.Errorf("...") if more than one did
 	return false, nil // nobody activated
 }