[ActivityIndicator] Add the onLayout prop to the outer container view

Summary:
ActivityIndicator was forwarding all of its props except `style` to the inner native view. This meant that onLayout would report a zero-sized frame that was relative to the wrapper view instead of the parent of the ActivityIndicator.

This diff adds `onLayout` to the wrapper view instead of the native view.

In general, all components that forward props need to be audited in this manner.

Closes https://github.com/facebook/react-native/pull/1292
Github Author: James Ide <ide@jameside.com>

Test Plan: `<ActivityIndicator onLayout={...} />` reports the size of the spinner plus a position relative to its parent view.

Libraries/Image/Image.ios.js

@@ -99,6 +99,12 @@ var Image = React.createClass({
      * testing scripts.
      */
     testID: PropTypes.string,
+    /**
+     * Invoked on mount and layout changes with
+     *
+     *   {nativeEvent: { layout: {x, y, width, height}}}.
+     */
+     onLayout: PropTypes.func,
   },
 
   statics: {