[auth] pass `repo` instead of `vreg` to SessionManager and AuthenticationManager Those object actually need a repo object to connect and create new session object. They used to retrieve the repo object using ``vreg.config.repository()``. I'm trying to sanitise the initialisation stack and get ride of ``config.repository()``, a function that mix factory and cache. Retrieving the vreg from the repo is trivial (``repo.vreg``) so we now pass the repo object instead of the vreg.

change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')