/**
  * What to do on plugin activation
  */
 public static function activate()
 {
     //ApmAddons::plugins_loaded() hook is not fired at plugin activation,
     //so we include addons file that may be needed in the following
     //"ApmTreeData::update_tree_data_on_install()" :
     ApmAddons::include_activated_addons_files();
     //Some pages may have been deleted/created/modified since last plugin install :
     ApmTreeData::update_tree_data_on_install();
 }