CORD-61 Dynamic XConnect support

- Add new XConnectConfig with unit test
- Gather XConnect features into XConnectHandler
- Introduce ObjectiveError.Type.GROUPREMOVALFAILED
- Rename
    - NetworkConfigEventHandler -> AppConfigHandler
    - XConnectNextObjectiveStoreKey -> XConnectStoreKey
    - Test json file
- Refactor

Change-Id: I8ca3176ed976c71ce9e28b7f3722ce80d49c816f
diff --git a/core/api/src/main/java/org/onosproject/net/flowobjective/ObjectiveError.java b/core/api/src/main/java/org/onosproject/net/flowobjective/ObjectiveError.java
index 8c20449..bd51902 100644
--- a/core/api/src/main/java/org/onosproject/net/flowobjective/ObjectiveError.java
+++ b/core/api/src/main/java/org/onosproject/net/flowobjective/ObjectiveError.java
@@ -34,11 +34,16 @@
     FLOWINSTALLATIONFAILED,
 
     /**
-     * THe group installation for this objective failed.
+     * The group installation for this objective failed.
      */
     GROUPINSTALLATIONFAILED,
 
     /**
+     * The group removal for this objective failed.
+     */
+    GROUPREMOVALFAILED,
+
+    /**
      * The group was reported as installed but is missing.
      */
     GROUPMISSING,