Pulling together hosting and renting

Added a test that rents and hosts a file, and verify that renting and hosting actually work. I don't verify that the host properly submits storage proofs though, that's on the way.

Unfortunately, there are now 2-3 problems with our test suite that only come up occasionally.

1. Sometimes transaction signing fails - this is what I'll be doing next.
2. Sometimes getting a block accepted fails - This is a problem with test synchronization. State subscription should actually fix this, though there are deeper issues regarding test synchronization
3. Sometimes the wallet will spend a timelocked output. This isn't a problem until you become a host and start freezing coins. This should be an easy fix.