Playout: New per-engine setboard_randomok setting

This is for a side-branch experiment where we generate some per-playout
settings for the Moggy playout policy.
Moggy ladderrate: Add a note about obsolescence
Moggy init: Do not set lcapturerate twice
Moggy init: Rearrange rates initialization by their default value
Moggy init: Also don't set nlibrate twice