adding purge option to IntentRemoveCommand

Change-Id: Ic97acd9a8308355cd3135ea5df0a470b3579106e
diff --git a/core/api/src/main/java/org/onosproject/net/intent/IntentService.java b/core/api/src/main/java/org/onosproject/net/intent/IntentService.java
index 0d14a38..b86d793 100644
--- a/core/api/src/main/java/org/onosproject/net/intent/IntentService.java
+++ b/core/api/src/main/java/org/onosproject/net/intent/IntentService.java
@@ -112,4 +112,11 @@
      * @param listener listener to be removed
      */
     void removeListener(IntentListener listener);
+
+    /**
+     * Purges a specific intent from the system if it is FAILED or WITHDRAWN.
+     *
+     * @param key key of the intent to purge
+     */
+    void purge(Key key);
 }