Bug 157174 [Viewers] Refactor new Viewer API
We are yet not completely happy with the API and refactor it.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/DecoratingLabelProvider.java
* returns <code>true</code>.
	 */
	public boolean isLabelProperty(Object element, String property) {
		if (getLabelProvider().isLabelProperty(element, property)) {
			return true;
		}
		if (decorator != null && decorator.isLabelProperty(element, property)) {
			return true;
		}
		return false;
	}
	/**
	 * The <code>DecoratingLabelProvider</code> implementation of this
	 * <code>IBaseLabelProvider</code> method removes the listener from both
	 * the nested label provider and the label decorator.
	 * 
	 * @param listener
	 *            a label provider listener
	 */
	public void removeListener(ILabelProviderListener listener) {
		super.removeListener(listener);
		getLabelProvider().removeListener(listener);
		if (decorator != null) {
			decorator.removeListener(listener);
		}
		listeners.remove(listener);
	}
	/**
	 * Sets the label decorator. Removes all known listeners from the old
	 * decorator, and adds all known listeners to the new decorator. The old