SCRUM#179 Add a DBus Daemon

Add a daemon to run edu-dbus when LE6 starts. The download method was changed from Util.spawn([]) to EduBus.download.StartRemote([]). The new method executes the download.sh script like the old one, but using a system dbus.

With these changes it's possible to adapt edu-dbus to add the future implementations of download methods. The download folder is shared between users, including guests.