[#791] cmd: Implement application observing storage engine

Implement skeleton of `neofs-lens` app which is going to be used for working
with storage engine's data.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

cmd/neofs-lens/root.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/nspcc-dev/neofs-node/misc"
+	"github.com/spf13/cobra"
+)
+
+var command = &cobra.Command{
+	Use:          "neofs-lens",
+	Short:        "NeoFS Storage Engine Lens",
+	Long:         `NeoFS Storage Engine Lens provides tools to browse the contents of the NeoFS storage engine.`,
+	RunE:         entryPoint,
+	SilenceUsage: true,
+}
+
+func entryPoint(cmd *cobra.Command, _ []string) error {
+	printVersion, err := cmd.Flags().GetBool("version")
+	if err == nil && printVersion {
+		fmt.Printf("Version: %s \nBuild: %s \nDebug: %s\n",
+			misc.Version,
+			misc.Build,
+			misc.Debug,
+		)
+		return nil
+	}
+
+	return cmd.Usage()
+}
+
+func init() {
+	command.AddCommand(
+	// sub-commands
+	)
+}
+
+func main() {
+	err := command.Execute()
+	if err != nil {
+		os.Exit(1)
+	}
+}