Remove ckan.authz

It has been removed in CKAN 2.0, trying to import it makes CKAN crash on
startup.

This means that get_top_packages() is broken, and needs to be rewritten
to work with CKAN 2.0. At least by removing the import the plugin can
be loaded and its other functions used but if you try to use
get_top_packages() it will crash.

ckanext/googleanalytics/dbutil.py

@@ -3,7 +3,6 @@ from sqlalchemy.sql import select, text
 from sqlalchemy import func
 
 import ckan.model as model
-from ckan.authz import Authorizer
 from ckan.model.authz import PSEUDO_USER__VISITOR
 from ckan.lib.base import *