Add a .go command to lod-util follow the first URI found attached to a predicate

e.g.,

```
> http://acropolis.org.uk/?for=http://www.bbcredux.com/%23members
:
:
> .go xhv:next
[Navigating to http://acropolis.org.uk/?for=http://www.bbcredux.com/%23members&offset=25]
:
:
```
