nixpkgs: torsocks 1.3 -> 2.0.0

Additionally, this fixes 'torsocks' using the 'which' executable as a
dependency.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixpkgs: tor depends on torsocks

This may seem strange, but tor distributes its 'torify' wrapper which in
turn attempts to use torsocks to bridge a connection, meaning 'tor'
users out the box may want it to work.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixos: rewrite torsocks module

Rather than trying to override the 'torsocks' executable in $PATH, the
new module instead properly configures `/etc/tor/torsocks.conf` and puts
the normal `torsocks` executable in $PATH so it can work out of the box.

As a bonus, I think this module actually works now, because the torsocks
configuration has changed a lot from when this was written, it seems...

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixos: overhaul Tor module

Signed-off-by: Austin Seipp <aseipp@pobox.com>