a miner actor is created with a choice of sector size

[laser]

Description

As per the spec, miner actors must be created with a sector size. This sector size can never change; all commitments will refer to sectors of the chosen size.

To begin with, the choice of sector size should be derived from the StorageMarketActor proofs mode. Miners should be created with the smaller sectors if the network is in proofs mode and should be created with larger sectors if not.

Note: We will eventually allow the miner operator to choose a sector size when creating the miner from the CLI.

Tasks

• Update StorageMarketActor#CreateMiner to use StorageMarketActor.ProofsMode to pick a SectorSize for the miner
• Update the Actor state to include SectorSize and create Actor#GetSectorSize
• Update Actor#SubmitPoSt and Actor#CommitSector to use SectorSize stashed in Actor.Storage

[laser]

Deleting this story in favor of A miner selects a sector size when pledging #2530.