Fix JsonBuilder setValues for nested arrays

This fixes the JsonBuilder setValues() function not following nested arrays when set with setOption().

```
$polyline = new Polyline();
$polyline->setOption(
    'icons', array(
        array(
            'icon' => array(
                'path' => 1
            ), 
            'repeat' => '75px', 
            'offset' => '100%')));
```

Currently the above produces:
```
{"map":map_52142b62cdbef,"path":[],"icon":{"path":1},"0":{"repeat":"75px","offset":"100%"}}
```

The fix corrects this to:
```
{"map":map_52142b62cdbef,"path":[],"icons":[{"icon":{"path":1},"repeat":"75px","offset":"100%"}]}
```