NCBC-652: Add support for bulk operations: Get and Upsert

Change-Id: Iae7e6f09f1e79f8782cf2d0c24bac3cb2f3d5598

Conflicts:
	Src/Couchbase/Core/IBucket.cs
Change-Id: I51fe6137468bcc863d594b346d241bc7709e3d07
Reviewed-on: http://review.couchbase.org/41723
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>