make user_id an accessor instead of just a reader

this allows the authenticated user to connect to other locations they are allowed to manage.
for example a google+ page they are set as Manager.  the authenticated user can override the
user id and set it to the google+ page id. they now can perform at least reading info.  I haven't
tested posting data since that's not a use case I have right now.
authenticate if needed before overriding the user_id
update version