Sia service daemons

[bschwand]

This is a port of the renterd, walletd and hostd daemons to participate in the Sia decentralized storage network. Hostd is tested in production, renterd has been tested too and I would welcome more FreeBSD users to test it out. Walletd is in beta and not recommended for production, this port allows FreeBSD users to test it out. I submitted a while a go a bug on bugzilla just for the hostd port, since then I was made aware of this repo and that many pull request have been issued against it for new ports, so I try this way instead as it is more convenient.