[wip]Making swarm query node always return checkin

@hbeeken , as discussed with @knolleary today, the query nodes will always have to return something. Therefore I modified the Swarm query node to ensure that its behaviour is consistent with what I implemented in the Instagram node.

Started working on this too as @hbeeken is out of office until Wednesday. Also did some tidy-up whilst I was there.

I expect the unit tests to fail (although the node looks to be working OK) so hence the WIP tag until I get those working.
@hbeeken my apologies. This wasn't my understand from discussions about it with Zoltán on Friday... must have got my wires crossed.

It should always return the most recent check in, regardless of when the node was deployed.