Refactor active model functionality for couchbase model

Change-Id: Ib96304de55d5bdae737513269f4fad5789cb38a2
Reviewed-on: http://review.couchbase.org/26822
Reviewed-by: Andrey Koleshko <ka8725@gmail.com>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>