Add RequestId, 4x4 logging and metrics

Adds logging of the following headers: `X-Socrata-RequestId` and `X-Socrata-4x4`.
Adds standard codahale metrics logging and graphite reporting for HTTP requests.
It would be nice to also be able to track how many actual rows are updated, I think this is tracking the number of "subversion" rows from the log table that get played back.  That may be harder though.