Properly map field names

Remap names to dbNames on criteria/fields/sort cursor options.

When setting fields for $query->sort() dbnames must be used instead of normaln names. This makes for inconsistent code where you have to use different names for different use cases:

```php
// normal name
$document->getProperty() 
// dbname
$query->sort([ 'prop' => 1 ]);
```

This is referenced in https://github.com/NextWebVentures/mandango/issues/3.