Up until now, this software has been focused on just Supporters, but
really there is no reason this should not be a general donor database.
Therefore, don't use the name supporter in the database, and add a
field.
public_ack is now allowed to be NULL, because the idea being we don't
have an answer from all who donate whether or not they want public
acknowledgment.
the is_supporter boolean is added to record whether or not they came
through the supporter program.
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