PyUtils+AthenaPython: Update CORAL attribute access for python 3.
Update the handling of CORAL attributes to work with both py3 and py2. Can simplify it now using a pyroot template proxy. Also remove reference to izip, which doesn't exist in py3.
Update the handling of CORAL attributes to work with both py3 and py2. Can simplify it now using a pyroot template proxy. Also remove reference to izip, which doesn't exist in py3.