Improve DST writer logic.

1. Only require the Turbo sequence passed if we're running in 'online'
mode *and* we're not running on simulated data. Otherwise, we want to
write out every event that's in the input.
2. Because of 1., we can no longer require the existence of
/Event/Turbo/Rec/Summary in the writer, because for events with no Turbo
lines firing the writer will still run but the summary will not be
made. This is a little unfortunate because we now have no run-time
guarantee that this location will be created when a Turbo line *does*
fire, as it should be, but I'm not sure of the alternatives.
3. Always write out the juggled raw event in online mode, because there
we always perform the juggling.