NCBC-533: Provide async/await Methods for Views

This commit adds expiremental/uncommitted support for asynchronous views 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: I2270aa633f7e0a17d99e171248097f2f2ade665e
Reviewed-on: http://review.couchbase.org/41854
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>