I should be able to revoke an Open Invitation

(User Story, Closed -> Duplicate, Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )

Summary: From the list of Open Invitations, I should be able to Revoke one of them. People who have already used it should be okay, but no one new can come in through it.

Depends Upon:

I should be see a list of my Open Invitations

Note that Open Invitations were designed with this story in mind. I believe that all it should take is removing the IsOpenInvitation flag from the Custom Role corresponding to this Open Invitation.