Persistent Host Consensus

Host now saves information that it parses from the consensus set, and will do a rescan in the event of desynchronization. This should shave 5 seconds off startup time on fast computers, and about 25 seconds on slow computers (perhaps 20% of the current startup time).

I also reorganized the persistence management quite a bit, changed the default price, and added test coverage for all the things I touched (minus mocking coverage).