[AETHER-1299] Implement SPINE pinning policy in SR.

Additionally introduces a new CLI command. Also this review addresses
comments coming from the previous patch [24393] and fixes some issue
seen in the previous patch.

Change-Id: I5362d95ebe1c237eb5bdb13ec34ab109d25f9f7a
diff --git a/impl/src/main/java/org/onosproject/segmentrouting/policy/impl/TrafficMatchKey.java b/impl/src/main/java/org/onosproject/segmentrouting/policy/impl/TrafficMatchKey.java
index 68181a6..44e618e 100644
--- a/impl/src/main/java/org/onosproject/segmentrouting/policy/impl/TrafficMatchKey.java
+++ b/impl/src/main/java/org/onosproject/segmentrouting/policy/impl/TrafficMatchKey.java
@@ -22,7 +22,12 @@
 import java.util.StringTokenizer;
 
 /**
- * Traffic match key used by the store.
+ * Traffic match key used by the store to track the operations ongoing on the devices.
+ *
+ * Traffic match is the high level intent expressed by the user that gets translated by
+ * the PolicyManager in modifications operated on the devices. The policy operations
+ * are more important than the policy itself without them the policy cannot be
+ * considered fulfilled.
  */
 public class TrafficMatchKey {
     private DeviceId deviceId;