router

An authentification layer is added on top of spice to authentify whoever is trying to attach to a VM.
Updated server and both nexush and nexus-cli accordingly.
The only visible change for users is that now client credentials to attach to a VM don't include a spice port and password, but only a single password.
Consequently the port column was removed from vmcreds2pdf/vmcreds2csv and the password is now a bit longer.
Server and client versions were bumped to 1.11.0.
WIP: nexus-exam