[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.
There was a node I reviewed a couple weeks ago that stored interval at a top level scope, meaning if you had two instances of the node, the second would overwrite the variable. This meant only one of the nodes interval would get cleared, the other continuing to fire in background.

I pointed this out and that interval needed to be stored within the scope of the node. Whether as a instance variable, or a local variable within a closure. I won't lose sleep over which approach is picked. The variant within a closure is marginally cleaner as it doesn't expose itself... but it feels a fairly academic argument. If the node defines a close method, rather than a 'close' event handler, then an instance variable is needed as a closure isn't possible...

A utility function on the prototype to create intervals might be interesting to look at... we could then automatically clear the interval on close.