Add labels to libconatiner config

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

libcontainer/configs/config.go

@@ -180,6 +180,9 @@ type Config struct {
 
 	// Version is the version of opencontainer specification that is supported.
 	Version string `json:"version"`
+
+	// Labels are user defined metadata that is stored in the config and populated on the state
+	Labels []string `json:"labels"`
 }
 
 type Hooks struct {