take into account schema.const also limit schema selection

jsonform/gadget_json_generated_form_child.js

@@ -393,7 +393,9 @@
     if (schema_arr.length === 1) {
       if (schema_arr[0].schema === true ||
           !(schema_arr[0].schema.hasOwnProperty('type') ||
-          schema_arr[0].schema.hasOwnProperty('enum'))) {
+          schema_arr[0].schema.hasOwnProperty('enum') ||
+          schema_arr[0].schema.hasOwnProperty('const')
+          )) {
         return false;
       }
       if (schema_arr[0].schema.type instanceof Array) {
@@ -522,7 +524,8 @@
           description = schema_item.title;
           if (schema_item.schema === true ||
               !(schema_item.schema.hasOwnProperty('type') ||
-              schema_item.schema.hasOwnProperty('enum'))) {
+              schema_item.schema.hasOwnProperty('enum') ||
+              schema_item.schema.hasOwnProperty('const'))) {
             generateItemsForAny(schema_item.property_name, schema_item.schema_path);
           } else if (getDocumentType(schema_item.schema.type) === "array") {
             description = description || schema_item.schema.description;