Debian packaging fixes
With this, we can build a Debian package for ideascube with the sbuild command, and with correct dependencies.
sbuild
allows building the package in a chroot, populated only with packages from the Jessie repos (which entirely avoids issues like the one @fheslouin regularly has with libjpeg), in a completely unattended and (almost) reproducible way.
This in turn will allow us to build packages in a Buildbot. And in fact, I have a local Buildbot which just successfully built a Debian package for Ideascube, which should make @barbayellow happy.