Web: port 80 may be occupied.

When I starting web server at:

``` bash
cd web
gulp build-app
node dist/server
```

I get an exception on line 9 dist/server.js where is listen on port 80. But port 80 may already be in use.

**Add the ability to specify the server to free the port number, normally default uses port 8080.**

**Recommendation**: enable source maps for better diagnostic error execution time.
