Adding error inspection of resource fetched by schema.php

Fixes up my previous PR https://github.com/codemix/restyii/pull/36 . In some cases the ```$config``` variable will hold a HTTP exception, and we need to catch this so as to enable more meaningful errors to be returned.

The patch will give me e.g.
```Error fetching 'productVariant'. CHttpException: Unable to resolve the request "productVariant/options".```

Instead of 
```exception 'CException' with message 'Property "Restyii\Client\Schema\Resource.code" is not defined.````