[ONOS-3634] Enhance app to have a category, icon, URL and readme

This commmit enhances application to have category, icon, URL and
readme. The web GUI and CLI will be implemented in separate commits

Change-Id: Ib02716d7118cc617b24f196f2213ea1fe99a34be
diff --git a/core/api/src/main/java/org/onosproject/app/ApplicationDescription.java b/core/api/src/main/java/org/onosproject/app/ApplicationDescription.java
index e8ff9ec..1528f35 100644
--- a/core/api/src/main/java/org/onosproject/app/ApplicationDescription.java
+++ b/core/api/src/main/java/org/onosproject/app/ApplicationDescription.java
@@ -44,6 +44,13 @@
     Version version();
 
     /**
+     * Returns the name of the application origin, group or company.
+     *
+     * @return application origin
+     */
+    String origin();
+
+    /**
      * Returns description of the application.
      *
      * @return application description text
@@ -51,11 +58,32 @@
     String description();
 
     /**
-     * Returns the name of the application origin, group or company.
+     * Returns category of the application.
      *
-     * @return application origin
+     * @return application category text
      */
-    String origin();
+    String category();
+
+    /**
+     * Returns url of the application.
+     *
+     * @return application url
+     */
+    String url();
+
+    /**
+     * Returns readme of the application.
+     *
+     * @return application readme
+     */
+    String readme();
+
+    /**
+     * Returns icon of the application.
+     *
+     * @return application icon
+     */
+    byte[] icon();
 
     /**
      * Returns the role of the application.