bind host support + searching local nodes ip library method

The bind host support is especially needed when developing with Vagrant (since you can't use Vagrants own network). In production you might also have a private network for the ES -traffic.

By default the bind_host isn't used, but if the attributes value is changed the library searches for the interface's ip and uses that. So no hard coded ip's. 

I also added the same interface support to the ES-host search.