Drop AlternativeHSAuthority and friends
We haven't had a notion of an HSAuthority since we dropped the v0 hidden service descriptor design completely back in 0.2.2. (See legacy/trac#10841 (moved) for more.) Specifically, in 0.2.2 or later, neither clients nor relays publish anything resembling a v0 hidden service descriptor, and "HS authorities" have nothing to do.
That said, we should drop the vestigial AlternativeHSAuthority option, since it has apparently has misled some folks into thinking that we do have HS authorities. (See legacy/trac#10722 (moved).)