Changes

Better AsyncJob implementation

Drops some concerns like the Result type which is just pushed down
into letting the concrete class do whatever it wants now.

This seems like it may fix the NRE that FuelFlowSimulation was
throwing from time to time which may have been some race condition
in the old BackgroundJob implementation that no longer exists?

Signed-off-by: Lamont Granquist <lamont@scriptkiddie.org>
 (commit: 1550c5f)