Define ID representation for Intent, IFlow and MatchAction

- Defines BatchOperationTargetId abstract class.
- The above class is the base class of IntentId, FlowId, and MatchActionId.
 -- Intent objects use IntentId class for its ID.
 -- IFlow objects use FlowId class for its ID.
 -- MatchAction objects use MatchActionId class for its ID.
- BatchOperation classes requires the BatchOperationTargetId as the target object's ID.
- This work is a part of ONOS-1758.

Change-Id: I71bb4e6acd3836d1ced3beb6fb331bca451abdc3
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/IFlowManagerService.java b/src/main/java/net/onrc/onos/api/flowmanager/IFlowManagerService.java
index edd3c85..ca4e5f7 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/IFlowManagerService.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/IFlowManagerService.java
@@ -31,7 +31,7 @@
      * @param id ID for IFlow object to be removed.
      * @return true if succeeded, false otherwise.
      */
-    boolean removeFlow(String id);
+    boolean removeFlow(FlowId id);
 
     /**
      * Updates IFlow object, calculates match-action plan and executes it.
@@ -50,7 +50,7 @@
      * @param id ID of IFlow object.
      * @return IFlow object if found, null otherwise.
      */
-    IFlow getFlow(String id);
+    IFlow getFlow(FlowId id);
 
     /**
      * Gets All IFlow objects.