Add 'norev' BLIP handler to log detailed error information

Couchbase Lite sends a 'norev' BLIP message when it is unable to send a revision.

 https://github.com/couchbase/couchbase-lite-core/blob/master/modules/docs/pages/replication-protocol.adoc#norev

As of today, Sync Gateway has no handler for norev messages, and just logs 'Unknown Profile' as part of the default handler.

We should have an explicit norev handler that logs the error/reason information sent, so that it is easier to diagnose issues from the logs.