[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.
As a side note, going with option (1) could be possible by sending a null payload when the user has not checked in since init. Therefore I personally think that option (1) could be OK but only if the additional null payload sending is ensured.

I personally prefer option 2 as its entirely stateless. We don't store initialization time. Initialization time raises all sorts of issues (timezone, etc.) that we would need to consider and maybe we don't want to at this stage. What are your thoughts @knolleary ?