NCBC-534: Provide async/await Methods for ad-hoc N1QL queries

This commit adds expiremental/uncommitted support for asynchronous ad-hoc
N1QL queries using async/await keywords. While it has been tested, it hasn't
been subjected to our larger suite of situational tests. Use at your own risk.

Change-Id: Idf905a09c255648d0b31dd75d8e6a854b50abe1f
Reviewed-on: http://review.couchbase.org/41855
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>