feat: placeholder for v1 subcommands (#135)

* feat: placeholder for v1 subcommands

* chore: more usage comments

cmd/influx/v1_commands.go

@@ -0,0 +1,14 @@
+package main
+
+import "github.com/urfave/cli/v2"
+
+func newV1SubCommand() *cli.Command {
+	return &cli.Command{
+		Name:  "v1",
+		Usage: "InfluxDB v1 management commands",
+		Subcommands: []*cli.Command{
+			newV1DBRPCmd(),
+			// etc
+		},
+	}
+}