tor: additional optional deps

Some additional optional deps for Tor.

Hopefully, sooner rather than later, libsodium will be an accepted alternative to nacl given it supplies many of the same headers.

Also removes the example file, as upstream regenerate it periodically and currently we don’t seem to respect that regeneration and leave outdated sample files in etc.

Adds a set of caveats about the ` torrc ` file, similar to the ones we have for ` clamav ` and others.