Bug 126414 [Commands] handlers: Provide help context ids
For commands and handlers to replace actions, they need to be capable of providing help context identifiers. For an example, see OpenResourceHandler in org.eclipse.ui.ide. This help context id will need to be definable through XML and through code.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/CommandManager.java
* The collection of execution listeners. This collection is
	 * <code>null</code> if there are no listeners.
	 */
	private ListenerList executionListeners = null;
	/**
	 * The map of parameter type identifiers (<code>String</code>) to
	 * parameter types ( <code>ParameterType</code>). This collection may be
	 * empty, but it is never <code>null</code>.
	 * 
	 * @since 3.2
	 */
	private final Map parameterTypesById = new HashMap();
	/**
	 * Adds a listener to this command manager. The listener will be notified
	 * when the set of defined commands changes. This can be used to track the
	 * global appearance and disappearance of commands.
	 * 
	 * @param listener
	 *            The listener to attach; must not be <code>null</code>.
	 */
	public final void addCommandManagerListener(
			final ICommandManagerListener listener) {
		addListenerObject(listener);
	}
	/**
	 * Adds an execution listener to this manager. This listener will be
	 * notified if any of the commands controlled by this manager execute. This
	 * can be used to support macros and instrumentation of commands.
	 * 
	 * @param listener