BigQuery client should support more OO interface

[TheKevJames]

Dealing with the JSON response objects is a nightmare. eg. for SELECT foo FROM bar, processing the response involves doing something like foos = [row['f'][0]['v'] for row in res.get('rows', [])]. Ideally, we'd be able to do foos = [row.foo for row in res] or such.

[BoweiYuanDialpad]

Indeed it's a very nice to have, not only for bigquery but also other services such as cloudtasks.