Add instructions for Running a Full Node as a Tor Hidden Service

[wbnns]

Bounty: 28,000 bits / ~$100 USD

It could benefit users if we had helpful step-by-step instructions describing how to run a full node as a Tor hidden service on the Running a Full Node page. Here are some resources to help get started:

• https://medium.com/@lopp/how-to-run-bitcoin-as-a-tor-hidden-service-on-ubuntu-cff52d543756
• https://www.reddit.com/r/Bitcoin/comments/4y7nc3/create_bitcoin_full_node_with_tor_step_by_step/?st=j5n7z1q1&sh=392084c9
• https://en.bitcoin.it/wiki/Setting_up_a_Tor_hidden_service

[theymos]

Note that I recently discovered that while method 2 on the wiki more-or-less works, Bitcoin Core's behavior was seemingly changed in more recent versions to not send addr messages for the hidden service component when connected to both Tor and the Internet. With the settings described on the wiki, it used to randomly send the hidden service ~75% of the time when doing addr messages, and your IP address ~25% of the time due to various interactions in the discovery/broadcast system. Maybe there's some setting that needs to be changed to fix this; I haven't looked into it much yet.