Add mailman passwords. One to the groups table to hold the admin
password for each project/group list, and another to the users table to hold each users password. These passwords are stored in cleartext. This is okay since the mailman password is deemed to be throw away since the mailman system is happy to mail them out to people in cleartext. We initially set them to a random value, and will provide a web interface on the Emulab side to change them. This is done in the mailman setup script though.