Add BitTorrent module (deluge-web).

This module can install and enable the Deluge web UI. It's available at /bittorrent. The application has a default password (deluge) but it asks the user to change it after first login.

deluge-web doesn't ship with an initscript yet (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=722719). So I included a button to start it manually if it's not already running.