Descendants of this class should implement the {@link init()} method and call the
{@link addSetting()} method for each of the plugin's settings.
For an example, see {@link Piwik\Plugins\ExampleSettingsPlugin\UserSettings}.
$userSettings = new Piwik\Plugins\ExampleSettingsPlugin\UserSettings(); // get instance via dependency injection
$userSettings->yourSetting->getValue();