[WIP][DO NOT MERGE] Proposal: Auto-scaling

Auto-scaling is a feature that allows users to increase capacity as needed by controlling the number of replicas deployed within the system based on request statistics. Auto-scaling is bidirectional, it will scale up to a specified limit as requests increase and scale down to minimal capacity as the requests decrease.

https://github.com/pweil-/origin/blob/035e0351a838a6ec6dcd65cc1977c85fca98ae5f/docs/autoscaling.md



It should be possible to write a custom auto-scaler and drive a replication controller without having to modify the existing auto-scaler.