Fix Last-Event-ID header handling for db changes feed
Fix Last-Event-ID header handling for db changes feed

This assumes Last-Event-ID header value to be opaque.

COUCHDB-2858

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb