init ucind CLI commands

cmd/ucind/cluster/root.go

@@ -0,0 +1,20 @@
+package cluster
+
+import (
+	"github.com/spf13/cobra"
+)
+
+const DefaultClusterName = "ucind-default"
+
+func NewRootCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "cluster",
+		Short: "Manage local Docker-based clusters.",
+	}
+	cmd.AddCommand(
+		NewCreateCommand(),
+		//NewListCommand(),
+		NewRemoveCommand(),
+	)
+	return cmd
+}