code: public static Configuration createCompositeConfiguration(final Class<?> clazz, final Configuration configuration) {
          final CompositeConfiguration compositeConfiguration = new CompositeConfiguration();
          final Configuration defaultConfiguration = ConfigurationFactory.getDefaultConfiguration();
          if (configuration != null) {
              compositeConfiguration.addConfiguration(configuration);
          }
          compositeConfiguration.addConfiguration(defaultConfiguration);
          return compositeConfiguration;
      }
docs: create a composite configuration that wraps the configuration sent by the
  user. this util will also load the "defaultConfig.properties" file loaded
  relative to the given "clazz" parameter
  
  @param clazz
  - the class that acts as referenced location of
  "defaultConfig.properties".
  @param configuration
  - the configuration supplied by the user that may override
  values in "defaultConfig.properties". If null is ignored.
  @return the created compsite configuration.