This is needed for #6372

New events:

• CoreUpdater.update.end

  Triggered after Piwik has been updated.

• PluginManager.pluginActivated - Parameters: $pluginName

  Event triggered after a plugin has been activated.

• PluginManager.pluginDeactivated - Parameters: $pluginName

  Event triggered after a plugin has been deactivated.

• Settings.$settingsName.settingsUpdated

  Triggered after a plugin settings have been updated. - Parameters: Settings $settings

  Example:

  Piwik::addAction('Settings.MyPlugin.settingsUpdated', function (Settings $settings) {
      $value = $settings->someSetting->getValue();
      // Do something with the new setting value
  });