Use onion service mirrors

[Phoul]

Use the Debian and Tor Project Onion Service package mirrors.

Debian and The Tor Project offer Onion Service Debian mirrors:

Debian
deb tor+http://vwakviie2ienjx6t.onion/debian jessie main
deb tor+http://vwakviie2ienjx6t.onion/debian jessie-updates main
deb tor+http://sgvtcaew4bxjd7ln.onion/debian-security jessie/updates main

Tor Project
deb tor+http://sdscoq7snqtznauu.onion/torproject.org jessie main

(#21 should be completed first)

[Phoul]

0127232 implements this for the Tor Project mirror.