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
* @param categoryId
	 *            The identifier to find; must not be <code>null</code>. If
	 *            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.