Starts the Scheduler's threads that fire {@link Trigger}s. When a scheduler is first created it is in "stand-by" mode, and will not fire triggers. The scheduler can also be put into stand-by mode by calling the standby() method.
The misfire/recovery process will be started, if it is the initial call to this method on this scheduler instance.
@throws SchedulerException if
shutdown() has been called, or there is an error within the
Scheduler.
@see #startDelayed(int)
@see #standby()
@see #shutdown()