Move new_authz.py into logic/auth/__init__.py

[seanh]

Makes sense to keep all auth stuff under logic/auth.

Also decide which functions from new_authz.pu should be marked private with _.

Also decide which functions from new_authz.py are really helpers for the auth functions in get.py, update.py and delete.py, and should maybe moved to another file, e.g. logic/auth/helpers.py