Provide stub for View's accessible prop (#558)

Because we didn't have any implementation for View's accessible prop, some
views were considered to be layout-only which weren't layout-only on iOS
and Android. The specific scenario I'm trying to fix is around touchables
(e.g. TouchableWithoutFeedback). I ran into a case where a touchable was
layout-only on Windows. When tapping it, React Native's JS code attempted
to measure the view. React Native was unable to return a result for the
measure request because the view that was being measured was layout-only.

React Native's JS sets accessible to true on touchables. According to the
React Native docs, "by default, all touchable elements are accessible."
(http://facebook.github.io/react-native/releases/0.30/docs/accessibility.html#accessible-ios-android)

By providing a stub implementation for the accessible prop, touchables
should never be layout-only on Windows thus fixing the measuring issue.

I opened issue #557 to track providing a proper implementation for the
accessible prop.

ReactWindows/ReactNative/Views/View/ReactViewManager.cs

@@ -22,6 +22,21 @@ public override string Name
             }
         }
 
+        /// <summary>
+        /// Sets whether or not the view is an accessibility element.
+        /// </summary>
+        /// <param name="view">The view.</param>
+        /// <param name="accessible">A flag indicating whether or not the view is an accessibility element.</param>
+        [ReactProp("accessible")]
+        public void SetAccessible(Border view, bool accessible)
+        {
+            // TODO: #557 Provide implementation for View's accessible prop
+
+            // We need to have this stub for this prop so that Views which
+            // specify the accessible prop aren't considered to be layout-only.
+            // The proper implementation is still to be determined.
+        }
+
         /// <summary>
         /// Set the pointer events handling mode for the view.
         /// </summary>