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.core.commands/src/org/eclipse/core/commands/CommandManager.java
*            the category is <code>null</code>, then a category suitable
	 *            for uncategorized items is defined and returned.
	 * @return The category with the given identifier; this value will never be
	 *         <code>null</code>, but it might be undefined.
	 * @see Category
	 */
	public final Category getCategory(final String categoryId) {
		if (categoryId == null) {
			return getCategory(AUTOGENERATED_CATEGORY_ID);
		}
		checkId(categoryId);
		Category category = (Category) categoriesById.get(categoryId);
		if (category == null) {
			category = new Category(categoryId);
			categoriesById.put(categoryId, category);
			category.addCategoryListener(this);
		}
		return category;
	}
	/**
	 * Gets the command with the given identifier. If no such command currently
	 * exists, then the command will be created (but will be undefined).
	 * 
	 * @param commandId
	 *            The identifier to find; must not be <code>null</code> and
	 *            must not be zero-length.
	 * @return The command with the given identifier; this value will never be
	 *         <code>null</code>, but it might be undefined.
	 * @see Command
	 */