This little-used debugging feature allowed you to SSH or Telnet "into" a
Tahoe node, and get an interactive Read-Eval-Print-Loop (REPL) that
executed inside the context of the running process. The SSH
authentication code used a deprecated feature of Twisted, this code had
no unit-test coverage, and I haven't personally used it in at least 6
years (despite writing it in the first place). Time to go.
Also experiment with a Twisted-style "topfiles/" directory of NEWS
fragments. The idea is that we require all user-visible changes to
include a file or two (named as $TICKETNUM.$TYPE), and then run a script
to generate NEWS during the release process, instead of having a human
scan the commit logs and summarize the changes long after they landed.
Closes ticket:2367
