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/Command.java
/**
	 * Adds a listener to this command that will be notified when this command
	 * is about to execute.
	 * 
	 * @param executionListener
	 *            The listener to be added; must not be <code>null</code>.
	 */
	public final void addExecutionListener(
			final IExecutionListener executionListener) {
		if (executionListener == null) {
			throw new NullPointerException(
					"Cannot add a null execution listener"); 
		}
		if (executionListeners == null) {
			executionListeners = new ListenerList(ListenerList.IDENTITY);
		}
		executionListeners.add(executionListener);
	}
	/**
	 * <p>
	 * Adds a state to this command. This will add this state to the active
	 * handler, if the active handler is an instance of {@link IObjectWithState}.
	 * </p>
	 * <p>
	 * A single instance of {@link State} cannot be registered with multiple
	 * commands. Each command requires its own unique instance.
	 * </p>
	 * 
	 * @param id
	 *            The identifier of the state to add; must not be