Rename numutil to typeutil

Change-Id: I5c215119d1e2cae07351860a0af088d01cfae913
Reviewed-on: http://review.couchbase.org/26364
Reviewed-by: Mordechai Nunberg <mnunberg@haskalah.org>
Tested-by: Mordechai Nunberg <mnunberg@haskalah.org>