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
The Default client lets specifying SSL be optional (defaulting to false), it might be good to preserve that pattern here.