Search / Sort by / Fix multiple fields

eg. `resourceTitleObject.${searchLang}.keyword,resourceTitleObject.default.keyword`

should create a filter

```
[
    {
        "resourceTitleObject.langdut.keyword": "asc"
    },
    {
        "resourceTitleObject.default.keyword": "asc"
    },
    "_score"
]
```

web-ui/src/main/resources/catalog/components/elasticsearch/EsService.js

@@ -203,6 +203,7 @@
           params.sort = [];
           sortBy.split(",", -1).forEach(function (value, idx) {
             if (value != "relevance") {
+              var sort = {};
               sort[getFieldName(mappingFields, value)] = orders[idx] || "asc";
               params.sort.push(sort);
             }