CBQE-1461/CBQE-1462: utf-16 encoded keys & values

- KV, XDCR tests
- Behavior subject to change
(based on decision of whether or not to support
non-utf-8)

Change-Id: I9396e3cac753dedccfba76f2fb37b98a6e1e0a25
Reviewed-on: http://review.couchbase.org/27360
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>