'Takes a string with the OutputPluginName, creates the object and
adds it to the OutputPluginName
:param output_plugin_name: The name of the plugin to add to the list.
:return: No value is returned.'

def _add_output_plugin(self, output_plugin_name):

    if (output_plugin_name == 'all'):
        file_list = os.listdir(os.path.join(ROOT_PATH, 'plugins', 'output'))
        str_req_plugins = [os.path.splitext(f)[0] for f in file_list if (os.path.splitext(f)[1] == '.py')]
        str_req_plugins.remove('__init__')
        for plugin_name in str_req_plugins:
            plugin = factory(('w3af.plugins.output.' + plugin_name))
            if (plugin_name in self._plugin_options.keys()):
                plugin.set_options(self._plugin_options[plugin_name])
            self._output_plugin_instances.append(plugin)
    else:
        plugin = factory(('w3af.plugins.output.' + output_plugin_name))
        if (output_plugin_name in self._plugin_options.keys()):
            plugin.set_options(self._plugin_options[output_plugin_name])
        self._output_plugin_instances.append(plugin)
