Metadata Semantics Too Verbose

The semantics for retrieving metadata seem rather verbose. In order to populate a Document I have I have to call the Meta function several times.

```c#
db.Query().Select(s => new Document
{
Id = N1QlFunctions.Meta(s).Id,
Cas = N1QlFunctions.Meta(s).Cas,
Content = s
}).First()
```

It really seems like there should be a way to just directly map the metadata to a Document or even better to properties on the POCO object. Something like the [BsonIdAttribute](https://mongodb.github.io/mongo-csharp-driver/2.7/apidocs/html/T_MongoDB_Bson_Serialization_Attributes_BsonIdAttribute.htm) in MongoDb.