Bugfix: config of failed,canceled tasks was not persisted
Javadoc, clearing our runNow behaviour
Protection for removed tasks and better "nextRun" calculation

As rescheduled tasks might have triggers changed. Still, unsure
in jobTrigger.getNextFireTime vs jobTrigger.getFireTimeAfter
call, as trigger is loaded from QZ, hence should be inited.
Undoing change

QZ guarantees that the method will return proper value,
the method does not work as long as trigger is not added to QZ