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 was intended to group it with other express middlewares