Remove references to non-existent objects

[thelastnode]

For example, users which are deleted being referenced by an org's attendance

[theJenix]

I think we need to be a bit careful with this one...if a user attended an event, we don't want to remove them from the attendance just because they deleted their account. Instead I propose we make that account "archived"..it still shows up in attendance logs where they signed in, but they cannot log in/the account is otherwise inactive. Otherwise, this presents a problem if we ever have to go back and verify attendance after the fact.

[thelastnode]

I agree

[thedekel]

the site isn't managing a massive amount of information per-user, and there's no way (that we know of) to see who is and isn't registered on the site, so deleting users is implemented in #169 as a way to remove test users and fake accounts.

closing this issue for the benefit of #170