Turn questions anonymous when user deletes their account

[pixeldesu]

Pitch

When a user deletes themself, instead of deleting all their questions (and all answers attached to them) instead null the user on the question and turn them anonymous.

Motivation

With a lot of deletions happening now, people are wondering where their answers are going, and since we don't have soft-deletes, this also gets rid of a bunch of content that people actually want to archive.