Bug 125420 [Commands] parameters: allow commands to specify return type
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/Command.java
public final ParameterType getParameterType(final String parameterId)
			throws NotDefinedException {
		final IParameter parameter = getParameter(parameterId);
		if (parameter instanceof ITypedParameter) {
			final ITypedParameter parameterWithType = (ITypedParameter) parameter;
			return parameterWithType.getParameterType();
		}
		return null;
	}
	/**
	 * Returns whether this command has a handler, and whether this handler is
	 * also handled and enabled.
	 * 
	 * @return <code>true</code> if the command is handled; <code>false</code>
	 *         otherwise.
	 */
	public final boolean isEnabled() {
		if (handler == null) {
			return false;
		}
		return handler.isHandled() && handler.isEnabled();
	}
	/**
	 * Returns whether this command has a handler, and whether this handler is
	 * also handled.
	 * 
	 * @return <code>true</code> if the command is handled; <code>false</code>
	 *         otherwise.
	 */
	public final boolean isHandled() {