NGI_pipeline working version

It is still under testing but it should be pretty stable: @mario please review it carefully
would be nice to know what exceptions can be raised and be more implicit. If you want to handle any exception and print it as you do here, you can use ```sys.exc_info``` as suggested [here](https://docs.python.org/2/tutorial/errors.html#handling-exceptions). Is not going to make a real difference so leave it as it is if you want.