Add GenericObject plugin files and assets

- Introduced default icon images in PNG and SVG formats.
- Added example icons for car and cube in SVG format.
- Created setup file for the GenericObject plugin with versioning and directory definitions.
- Included a header file with licensing information for the plugin.
- Added a remove.txt file with instructions for safe deletion.

plugins/genericobject/inc/singletonobjectfield.class.php

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * -------------------------------------------------------------------------
+ * GenericObject plugin for GLPI
+ * -------------------------------------------------------------------------
+ *
+ * LICENSE
+ *
+ * This file is part of GenericObject.
+ *
+ * GenericObject is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GenericObject is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GenericObject. If not, see <http://www.gnu.org/licenses/>.
+ * -------------------------------------------------------------------------
+ * @copyright Copyright (C) 2009-2022 by GenericObject plugin team.
+ * @license   GPLv3 https://www.gnu.org/licenses/gpl-3.0.html
+ * @link      https://github.com/pluginsGLPI/genericobject
+ * -------------------------------------------------------------------------
+ */
+
+// ----------------------------------------------------------------------
+// Original Author of file: Walid Nouh
+// Purpose of file:
+// ----------------------------------------------------------------------
+if (!defined('GLPI_ROOT')) {
+   die("Sorry. You can't access directly to this file");
+}
+
+class PluginGenericobjectSingletonObjectField {
+   /// Items list
+   static $_dbfields = [];
+
+   /**
+    * Singleton to store DB fields definition
+    *
+    * @since 2.1.0
+    * @param itemtype itemtype to query
+    * @param reload reload db fields configuration from DB
+    *
+    * @return an array which contains DB fields definition
+    */
+   public static function getInstance($itemtype, $reload = false) {
+      global $DB;
+      if (!isset(self::$_dbfields[$itemtype]) || $reload) {
+         self::$_dbfields[$itemtype] = $DB->listFields(getTableForItemType($itemtype));
+      }
+      return self::$_dbfields[$itemtype];
+   }
+}
+