Bug 204458 [Commands] Allow menu and toolbars to fire execution events
Keybindings will currently fire execution events when executing actions from the action framework. i.e. IActions with their actionDefinitionId set and IActionDelegates with the definitionId attribute in their action contributions. But it would be nice if selecting the menu or tool item would also fire the equivalent events. PW
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ExternalActionManager.java
* 
		 * @param identifier
		 *            The identifier of the item to from the listener should be
		 *            removed; must not be <code>null</code>.
		 * @param listener
		 *            The listener to be removed; must not be <code>null</code>.
		 */
		public void removePropertyChangeListener(String identifier,
				IPropertyChangeListener listener);
	}
	/**
	 * The singleton instance of this class. This value may be <code>null</code>--
	 * if it has not yet been initialized.
	 */
	private static ExternalActionManager instance;
	/**
	 * Retrieves the current singleton instance of this class.
	 * 
	 * @return The singleton instance; this value is never <code>null</code>.
	 */
	public static ExternalActionManager getInstance() {
		if (instance == null) {
			instance = new ExternalActionManager();
		}
		return instance;
	}
	/**
	 * The callback mechanism to use to retrieve extra information.
	 */
	private ICallback callback;