Stop setting an email address on tutorial accounts

[ahelsing]

Currently we create email accounts for tutorial accounts. These emails do not go to the experimenter.
Going forward, we won't be creating any such email accounts. So emails to these addresses would just bounce.

Instead, leave the email address blank. Then the experimenter can self-assert their own real email address when they get to the portal.

[ahelsing]

Note that this requires:

• ensure no geni-ar code dies if an account has no email address
• clearinghouse database queries that try to ID tutorials by email address must do something different (use EPPN and/or affiliation)

Also note that these users, as before, cannot use our IdP to reset their IdP password or recover their username, as they have no email. (Before there was an email address they couldn't read.)

[ahelsing]

Note this requires a schema change to allow the email address field to be null on account requests.

[ahelsing]

Will also include the name of the tutorial organizer in the email to the organizer (cc'ed to admins).