Limit displayed logged errors in admin.
Ensure indexes everywhere where we sort.
Correctly generate display name for persons who are not users.
Use Docker linking instead of Skydock.
Enqueue Tumblr job only on workers.

This is still not ideal as many workers going up and down could be
postponing the event into the future all the time (because they cancel
existing event and add a new one), but it is still better than any
instance doing that.
Don't stop processing jobs if there was a race condition.
Style.
Added distributed updating of all references.
Updated PeerDB for better error messages.
Don't use class names directly.

They get minimized in production and things don't work anymore. This is
why we have Meta._name for example. In this case it is even better to
use directly a collection name.
Style.