R1:a600ab77316f

Prevent administrators from locking themselves out of applications

Summary: Ref T603. This could be a nicer UX, but limit the amount of foot-shooting that users can possibly do. You can still manage if you're really tricky ("Members of project X", then leave the project) but this should make it hard to make a mistake. It seems very unlikely any user ever intends to lock themselves out of an application.

Test Plan: Set an application's view policy to permissive ("Administrators") and nonpermissive ("No…