IO Namespace refactoring and support for async/await

Change-Id: I38b1dae90f0c7d4400f88b4dc460c8fd41e8c20c

Conflicts:
	Src/Couchbase/Couchbase.csproj
	Src/Couchbase/IO/Operations/IOperation.cs
Change-Id: I0d66352d1e975d427504b7fc525e4539cae435b5
Reviewed-on: http://review.couchbase.org/43452
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>