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
*            <code>null</code> if the command does not declare a return
	 *            type.
	 * @since 3.2
	 */
	public final void define(final String name, final String description,
			final Category category, final IParameter[] parameters,
			ParameterType returnType) {
		if (name == null) {
			throw new NullPointerException(
					"The name of a command cannot be null"); 
		}
		if (category == null) {
			throw new NullPointerException(
					"The category of a command cannot be null"); 
		}
		final boolean definedChanged = !this.defined;
		this.defined = true;
		final boolean nameChanged = !Util.equals(this.name, name);
		this.name = name;
		final boolean descriptionChanged = !Util.equals(this.description,
				description);
		this.description = description;
		final boolean categoryChanged = !Util.equals(this.category, category);
		this.category = category;
		final boolean parametersChanged = !Util.equals(this.parameters,
				parameters);
		this.parameters = parameters;
		final boolean returnTypeChanged = !Util.equals(this.returnType,
				returnType);
		this.returnType = returnType;