add TODO about parameters to the background thread start()
remove TODO about success bool in BackgroundJobFinished

A boolean result isn't very useful, and violates the
general idea of no results from background jobs.
People can send events if they need to.
Define run and runMain in terms of backgroundRun and backgroundRunMain

These don't work as of this commit because jobWaitFor is broken.
In jobWaitFor and jobStop, don't rely on possibly-stale jobList

It seems we were getting a list that was no longer valid,
since the list of jobs is mutable.
In run/runMain, use jobService.waitFor directly, not jobWaitFor task

Can't figure out how to invoke the jobWaitFor task.