[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.
I'm not sure why "interval" is added onto the node (as well as afterTimestamp and lastcheckin). Looking through the other nodes available they all keep them as a var. @knolleary - what is the convention here or reasons for/against? I'm not sure I understand the benefits/ramifications either way.