core/gadget_global.js: change rules of asBoolean to match python rules

 - no more "false" string false
 - empty arrays are false

"false" string evaluating as false allowed to use ?editable=false
in the URL to force a page to render as non editable. This was probably
used only in the tests. The support of this was moved to the form page
gadget.

bt5/erp5_web_renderjs_ui/PathTemplateItem/web_page_module/rjs_gadget_erp5_page_form_js.js

@@ -182,8 +182,8 @@ and handling data send&receive.
           is_refresh: options.is_refresh || false
         };
 
-      // options.editable differs when it comes from the erp5_launcher of FormBox - try to unify it here
-      if (asBoolean(options.editable)) {
+      // options.editable differs when it comes from an option in URL param, from erp5_launcher of FormBox - try to unify it here
+      if (options.editable !== "false" && asBoolean(options.editable)) {
         options.editable = 1;
       } else {
         options.editable = 0;

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/gadget_global.js.js

@@ -47,18 +47,17 @@
   }
   window.getFirstNonEmpty = getFirstNonEmpty;
 
-  /** Convert anything to boolean value correctly (even "false" will be false)*/
+  /**
+   * Convert anything to boolean value with rules similar to python.
+   */
   function asBoolean(obj) {
     if (typeof obj === "boolean") {
       return obj;
     }
-    if (typeof obj === "string") {
-      return obj.toLowerCase() === "true" || obj === "1";
-    }
     if (typeof obj === "number") {
-      return obj !== 0;
+      return Boolean(obj)
     }
-    return Boolean(obj);
+    return !isEmpty(obj);
   }
   window.asBoolean = asBoolean;