[New] Added New l10n_it_base refactored and new l10n_it_pec

Hi!
as discuss on https://github.com/OCA/l10n-italy/issues/2 I made this pull request.

The l10n_it_base now is a simple configuration module.
I created a l10n_it_pec that add a field for mail on the partner profile after the normal mail

Regards

Franco
Is the priority needed?