ONOS-1684 Added support for app dependencies.

Change-Id: Iae318c24c3c9bd43d84318c79ac420fc85d5d599
diff --git a/core/api/src/main/java/org/onosproject/core/Application.java b/core/api/src/main/java/org/onosproject/core/Application.java
index fca5384..ea2eab9 100644
--- a/core/api/src/main/java/org/onosproject/core/Application.java
+++ b/core/api/src/main/java/org/onosproject/core/Application.java
@@ -84,4 +84,11 @@
      * @return application features
      */
     List<String> features();
+
+    /**
+     * Returns list of required application names.
+     *
+     * @return list of application names
+     */
+    List<String> requiredApps();
 }