code: static Object createObject(String factoryId, String fallbackClassName)
          throws ConfigurationError {
          return createObject(factoryId, null, fallbackClassName);
      }
docs: Finds the implementation Class object in the specified order.  The
  specified order is the following:
  <ol>
  <li>query the system property using <code>System.getProperty</code>
  <li>read <code>META-INF/services/<i>factoryId</i></code> file
  <li>use fallback classname
  </ol>
  
  @return instance of factory, never null
  
  @param factoryId             Name of the factory to find, same as
  a property name
  @param fallbackClassName     Implementation class name, if nothing else
  is found.  Use null to mean no fallback.
  
  @exception ObjectFactory.ConfigurationError