[feature request] change attendee status

[ultrasaurus]

Sometimes we'll have someone sign-up who self-identifies as someone not from the target outreach group, and it seems like a reasonable tactic is to move them to the waitlist or ask them to volunteer if there is a need (e.g. come early and help with registration or stay late and cleanup)

In #633, @jr0cket asks:
Q: Is there a way to waitlist a student that signed up as male and has no plus one under-represented type?

Proposal: change "Attending students and volunteers" ...

In Organizer Console, when an organizer clicks "Show all Attendee RSVP Details"

the "Attending students and volunteers" page is displayed, which allows removing an RSVP. Instead, we could make it so there's an "Action" menu...

Which could include:

• "Move to Waitlist" (not sure what the inverse of this is, maybe "Move from Waitlist to Accepted")
• "Change to Student" or "Change to Volunteer" (to swap student/volunteer)

(also might be friendlier to change "Destroy" to "Remove")

Ideally there should be some kind of confirmation that says the organizer should have already separately communicated with this person

[ultrasaurus]

Also, this feature request seems somewhat related: #456

[ultrasaurus]

@rachelober we should look at this PR before working on this: #481