Add TLS to peer-to-peer connections

The goal is to improve privacy by making packet inspections a lot harder. In countries where cryptocurrencies or anonymous cryptocurrencies are illegal, this could be very important.

Ulttimately we could use Kovri or something similar, but this gets us 80% there for almost no performance penalty with what should just be very little code.

To preempt some comments about TLS security (which isn't great), this is only for privacy and we can support only a very small subset of known good cyphers.