Tasks stop on unmanaged

stop tasks when entities are unmanaged, and better bookkeeping for scheduled tasks.
(also fixes eclipse IDE problems caused by checkstyle.)
Again, I'd prefer `Asserts.succeedsEventually(new Runnable() {...})` with appropriate `assertEquals` etc in the runnable impl. I see no reason to specify ten second timeout, or to not just rely on the nice backoff behaviour we have in our `Asserts` code (except to limit logging to at most once every 20ms).