It will show a sparkline image, the value of the resolved metric name and a descrption. Optionally, multiple
values can be shown after a sparkline image by passing multiple metric names
(eg array('nb_visits', 'nb_actions')). The data will be requested from the configured api method see
{@link Piwik\ViewDataTable\RequestConfig::$apiMethodToRequestDataTable}.
Example:
$config->addSparklineMetric('nb_visits');
$config->addTranslation('nb_visits', 'Visits');
Results in: [sparkline image] X visits
Example:
$config->addSparklineMetric(array('nb_visits', 'nb_actions'));
$config->addTranslations(array('nb_visits' => 'Visits', 'nb_actions' => 'Actions'));
Results in: [sparkline image] X visits, Y actions