Data fields can be subfields or array elements

GridColumns can be like that :

```javascript
	var columns = [
			{ id: "ip", name: "IP", field: "nics[0].ip", sortable: true },
			{ id: "schema", name: "SCHEMA", field: "resourceSchema.name" },
			{ id: "kapi", name: "KAPI", field: "kuark.alias" },
		];
```
getDataItemValue parses item field, recursively.