Merge branch 'tox' into 'belenos'

Add Tox (http://tox.im) packages

Tox is a decentralized distributed (no servers) instant messaging app with built-in encryption, audio/video support, file sharing, group chat and more. So far there has been no way to install the various Tox client applications on ubuntu or Trisquel without compiling from source or using a PPA. Although in development and some features aren't complete, they are already usable and useful.

Order of dependencies:

1

- filteraudio, dependency library of qTox
- libsodium, dependency library of toxcore

2

- toxcore, dependency of all Tox clients below

3

- Toxic (ncurses terminal client)
- uTox  (lightweight GUI client using libx11)
- qTox  (GUI client using Qt)

See merge request !32