Enforce SafeLogging on the console.

Previously we always assumed that the console was ephemeral, and so we disabled safe logging. But the console can be piped to journald. And even if we enforce isatty there's no guarantee that the user isn't using some kind of terminal that logs to disk or something.

Best just to enable SafeLogging unconditionally. I've added a note about where and how we might re-enable this.

Closes #553 (closed).