Mnior makeup --kazu
ADDITION + BUG FIX:

    (*) Introduced cluster class in SimpleTree fmwk
    (*) Bug fix in initialization loop.

    This version is tested with DataFormat/mac/simple.py which essentially
    creates data container class instance & initialize @ loop beginning and end.
    Speed optimization confirmed to work well in clear_event() method.

Kazu
ADDITION + MINOR:
	 (*) Added mcnu class to hold MCNeutrino information
	 (*) Minor decoration

Kazu