removing dependency on n1ql from common/ package.

moving into protobuf/ sub-package since evaluation is done here.

Change-Id: I08596711b0eed3acb3c95b6657ce2b9aa6babee6
Reviewed-on: http://review.couchbase.org/43675
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>