Interfaces instead of Handlers?

[nickcapurso]

The NetworkTimeout, JSONFetcher, and PlanningModule classes all use Handler references to notify clients of finished events. Alternative method would be to use interfaces and callbacks (which, arguably, would be faster) - need to examine whether this is feasible.

Sticking with Handlers would be good if any of these will be done in background threads in the future (and events are needed to be sent to the UI thread).