logs can be sent as json

If you request the couchdb logs (http://127.0.0.1:5984/_log). I want the option of getting them returned in json format. This makes it much easier to work with the logs in javascript.  

`curl http://127.0.0.1:5984/_log?format=json` for JSON log output.

I've added the format="json" q-value for when the request wants it to be formatted in json. Hopefully there is a better way of doing this.