Added helper methods to fire status change events
Changed to use EventBus for handling job events

Changed the backend implementation for handling job status events to use
Guava EventBus subscription technique instead of an event listener
model.
Changed to use EventBus for handling status event

Changed application to use singleton Guava EventBus to post status
change events. This replaces the status change listener and event design
used previously.
Removed unnecessary code from jobs
Update StatusOutputTab only on the EDT