Allow POST to _log.
Allow POST to _log.

POST /_log {"level":"info|debug|error", "message":"your message here"}

Patch by Robert Newson.

Closes COUCHDB-464

smithsz/couchdb-couch,KlausTrainer/couchdb-couch,fkaempfer/couchdb,cloudant/couchdb-couch,cloudant/couchdb-couch,fkaempfer/couchdb,cloudant/couchdb-couch,alanning/couchdb-couch,fkaempfer/couchdb,alanning/couchdb-couch,smithsz/couchdb-couch,fkaempfer/couchdb,KlausTrainer/couchdb-couch,ngpestelos/couchdb-couch,KlausTrainer/couchdb-couch,apache/couchdb-couch,ngpestelos/couchdb-couch,fkaempfer/couchdb,alanning/couchdb-couch,apache/couchdb-couch,fkaempfer/couchdb,apache/couchdb-couch,smithsz/couchdb-couch,ngpestelos/couchdb-couch