Feature 17178 v5 rebased
Add experimental OnionServiceSingleHopMode and OnionServiceNonAnonymousMode options.
Implements proposal #260, completes ticket #17178. Patch by teor & asn.
Hidden services opportunistically upgrade to rend point ntor onion keys from relay descriptors.
Related to ticket #19163, bugfix on Tor 0.2.4.8-alpha.
Prevent Tor2web clients running hidden services, these services are not anonymous due to the one-hop client paths.
Fixes bug #19678. Patch by teor.