Don't filter actor members on stop_date

Another Focus quirk. It looks like some members have stop_date set.
We're not 100% sure of the semantics of this, but it probably means that
their membership isn't paid. We still want to find and see those users.

However, in commit a711cbf62 I filtered the Actor.membership_type()
method on stop_date. This was as far as I can remember because some
members have multiple membership services, e.g. when they age, but
instead of deleting the old one, stop_date is set.
Refactor 'personal memberships' for semantics
Expire the users cache when creating new forening
Complete transaction first when result is stored
Skip forening if the user is pending
Verify ajax POST params