Add functionality for manual subscription to lists

For example, RLC gets to be on members list. Just add someone to the
table:

```
mysql> describe updating_email_lists_additions;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| listname | varchar(20) | NO   | PRI |         |       |
| email    | varchar(64) | NO   | PRI |         |       |
+----------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
```