Bug 153933 [Dialogs] [RCP] Dialog.DLG_IMG_HELP not available in RCP apps
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/JFaceResources.java
*            the symbolic name of the image
	 * @param path
	 *            the path of the image file relative to the base of the
	 *            workbench plug-ins install directory
	 * @param fallback
	 *            the {@link Class} where the fallback implementation of the
	 *            image is relative to
	 * @param fallbackPath
	 *            the path relative to the fallback {@link Class}
	 * 
	 */
	private static final void declareImage(Object bundle, String key,
			String path, Class fallback, String fallbackPath) {
		
		ImageDescriptor descriptor = null;
		if (bundle != null) {
			URL url = FileLocator.find((Bundle) bundle, new Path(path), null);
			if (url != null)
				descriptor = ImageDescriptor.createFromURL(url);
		}
		
		if (descriptor == null)
			descriptor = ImageDescriptor.createFromFile(fallback, fallbackPath);
		imageRegistry.put(key, descriptor);
	}
	/**
	 * Returns the resource object with the given key in JFace's resource
	 * bundle. If there isn't any value under the given key, the key is
	 * returned.
	 *