Fix config.json and add favicon support

/to @bajtos or @ritch 

The PR fixes 3 issues:
- Make sure the app is listening on 0.0.0.0:3000 instead of localhost:3000
- Add favicon middleware to avoid 404 warnings
- Fixes https://github.com/strongloop/generator-loopback/issues/12
I think the URL that is printed out should **always** be generated from what the server actually binds to (with 0.0.0.0 replaced with localhost for the Windows folks) and that if a URL is given it should be decomposed and used to specify the host and IP to listen on with the individual host and port settings overriding those values.

port = process.env.PORT || config.port || config.url.port || 0;
host = config.host || config.url.host || '0.0.0.0';