Many improvements. QR code, fixed page size, better
use of page estate, etc.
Also pdfkit should kind of work now (not quite using
the full page size, but at least it's not utterly
broken like before).
Most parameters used by the Jinja template for the cards
can now be specified in settings.yaml. This should make
the generation of cards for admin training much easier.
This allows to manage groups of VMs across multiple infrastructure
providers. It also adds support to create groups of VMs on OpenStack.
WARNING: the syntax of workshopctl has changed slightly. Check READMEs
for details.
