Cleaning up Javadocs in core-ui classes.
Promoted Glyphs inner class to GlyphConstants.

Change-Id: Ib12a4556a75d98edb3544b9ae45605fab554fdcf
diff --git a/core/api/src/main/java/org/onosproject/ui/UiExtensionService.java b/core/api/src/main/java/org/onosproject/ui/UiExtensionService.java
index d0004d2..79114e0 100644
--- a/core/api/src/main/java/org/onosproject/ui/UiExtensionService.java
+++ b/core/api/src/main/java/org/onosproject/ui/UiExtensionService.java
@@ -25,19 +25,19 @@
     /**
      * Registers the specified user interface extension.
      *
-     * @param extension GUI extension to register
+     * @param extension UI extension to register
      */
     void register(UiExtension extension);
 
     /**
      * Unregisters the specified user interface extension.
      *
-     * @param extension GUI extension to unregister
+     * @param extension UI extension to unregister
      */
     void unregister(UiExtension extension);
 
     /**
-     * Returns the list of user interface extensions.
+     * Returns the list of registered user interface extensions.
      *
      * @return list of extensions
      */
@@ -47,7 +47,7 @@
      * Returns the user interface extension that contributed the specified view.
      *
      * @param viewId view identifier
-     * @return user interface extension
+     * @return contributing user interface extension
      */
     UiExtension getViewExtension(String viewId);
 }