List-of-emails widget for invite new users

[Paul Everitt]

As moderator, go to a community and click Members. You'll see an action "Invite New" that leads to karl.views.members.invite_new_user_view.

This view uses the karl.views.members.InviteNewUsers form. The email_addresses field is a textarea returning a string. We need a validator:

- Return a list of unicode strings

- Strip space on each line

- Don't return empty lines

- Raise a validation error if:

  o Empty

  o One of the lines doesn't look like an email address (using FormEncode.validators.Email or something similar)

[Paul Everitt (paul-agendaless)]

If this is quick, let's do this soon.