Added method waitForEmpty() for better synchronization between Jobs
(Shell and other).
Added automatic flush for STDpipes when ending.
Added methods for checking StdIN and StdOUT for jobs.
Now Jobs waits for flushing STDpipes when he finished work. 

Added cleanAfterJob(): Job can do any pending operations when finished /
SIG_KILLed

Added childHasEnded(): Tells the Job that his child has ended.
Improved Job Echo.
Now the children tell theirs parents when they die.