Update Global Settings

@mdaines-r7 (@defndaines) Can you check this PR out? I'd like to get it merged for some automated tests I'm working on right now.
Heh heh, so it's OK for the `Connection` object to violate SRP? ;^)

If we had a nice clean interface to the product, that wasn't spread out over many versions, then it might make sense to separate the serialization of the configuration objects from the manipulation of the configuration objects, but that's just not the case with Nexpose (and won't be anytime in the next year or two). So as it stands, the `Connection` is require to communicate to a console. The pattern is to call methods on the `Connection` to get information or invoke actions (starting scans). Otherwise, configuration objects are used to load data from across a `Connection` and then save it back.

Once you pull out this method, I can merge and push a new version of the gem.

(The `sites` method returns `SiteSummary` objects.)