initial BasicAuthExhibitorRestClient 

that can also skip ssl cert validation if required

Also might be nice to provide a convenience method in ExhibitorEnsembleProvider, something like

```java
pubic static ExhibitorEnsembleProvider fromURL(URL vip, boolean validateSsl)
```

which would create the `Exhibitors` from the hostname, extract the userInfo, port and path from the url
I'm not sure this cast is necessary, I think the connection can be a plain URLConnection for how we use it.