Fix mining front end

Except for siac. Siac is probably super broken.

I also disabled all of the hosting and renting javascript, so none of that should work any more, though there might be something I forgot to comment out.

I also found out that alll gothreads run in one kernel process, using only 1 CPU core, unless you explicitly increase the number of kernel processes that golang is allowed to use, which is why go threads are so lightweight. So now when you mine on multiple threads, I allocate one kernel process for each thread.

The details are explained in package `runtime`.

I'm also slowly but surely building out the test suite so that when things are incorrect we know right away.