Miner polish

I finished polishing up the miner, including adding api calls for external miners, and adding 'hashrate' and 'blocks per month' to the miner info struct.

All that I feel remains is removing the multi-threading, which I refuse to do until cpu mining is utterly worthless. As long as a desktop cpu can find blocks occasionally on p2pool, it's worthwhile to me to keep the multithreading around.

If you read the extended message of the first commit, you see that I've started triggering the race detector. I do believe that this problem has been there the whole time, I can't really figure out why it would start complaining now. Also, it seems like it's a false positive, I'm not sure why it's complaining or how to make it stop.

I'll give it a closer look later on, but for the time being I'm not too worried.