Host, Renter, State subscriptions

I reimplemented host and rent. Host now works by subscription, and should work a decent amount better than before (meaning less bugs when submitting storage proofs). There are still an handful of problems, but these are detailed in a series of TODOs.

I implemented renter so that you upload to multiple places and then download from multiple places. So there's naive redundancy happening. At the moment there is no file repair whatsoever. That should be alright for now.

I had to add a subscription based model of passing out updates to the state. Overall, I think that this is very much the right thing to do. Unfortunately, I didn't have time to completely fix how the state works to accommodate this. So the subscription updates actually give incomplete and misleading information, but in such a way that the host (who is currently the only one using the subscription stuff) is completely unaffected (... at least... I think).

The code was basically just shoved into place. I will go back and make it nice, and on the way probably remove a ton of complicated code from the state that won't need to be there anymore (like I said, this change makes sense for a lot of reasons). This will take me a lot of time, and won't be done by release which is why I chose to just shove things together for the time being. I'll clean it up afterwards.