Implement the "shortest queue" load balancing

[nikolay]

https://labs.spotify.com/2015/12/08/els-part-1/
https://labs.spotify.com/2015/12/09/els-part-2/

[kessler]

This one and #1 are both types of priority queues. Which are on the roadmap

[nikolay]

@kessler Yes, thank you!