Partially implementing this as part of my work on T401: Post list paging and T714: Improve core navigation.

Getting much more important as Write.as grows past 500k posts on the platform.

To add to this list:

This is looking really good so far! Have been using it myself lately and it's been great.

As discussed in #174, this is now the "silence" admin feature. See that PR for remaining items needed to resolve this.

Addressed in writefreely#189.

Note: implementation details are out of date and only apply to Write.as. For implementation in WriteFreely, refer to [deleteAccount()](https://phabricator.write.as/diffusion/W/browse/master/database.go$2674) func in rW.

{T706} solves our immediate needs for #write.as_for_teams, so we'll do that first. Then we can look at addressing this.