JCBC-633: Add Iterator to sync ViewResult

Motivation
----------
Adding an iterator to ViewResult allows for nice for() syntax, without
having to pull out the iterator manually.

Modifications
-------------
Adds the Iterator<ViewRow> interface to the ViewResult and implementation,
just proxying through to the rows() automatically.

Result
------
More streamlined use of ViewResult and rows when iterating sync.

Change-Id: I573da4e94c1cdc7c2a9ebc35af654a3ba5bae5be
Reviewed-on: http://review.couchbase.org/43557
Reviewed-by: Simon Baslé <simon@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>