Add control board model to MinerData

[cryptographicturk]

As a large scale miner we have a variety of different control boards that has come with all of our equipment. Where it's possible to know, we would like a string that identifies each control board in the MinerData. Some of the firmware API's provide this information, and it's possible to parse it out of the log files on the stock bitmain miners.

[b-rowan]

Ideally I would prefer not to parse log files for this information, I can check elsewhere for it on stock FW, but loading log files implicitly seems like a bad idea, as they can contain a very large amount of data.