stateless client: almost completed. Still needs to fix an issue with automatically removing CA certificate when remote-viewer exits

Updated firewall rules in live-exam iso image generator

Updated the docs accordingly (for now this part is not documented).

install.md: added section on how to build a static version of nexus-exam
nexus-exam: decreased window height to be less ugly

Updated docs/install.md accordingly.
Better commented nexus-server's qemu settings.

Fixed a bug in Makefile where password with some special chars wasn't handled correctly

User exam credentials are now embedded into nexus-exam

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

Had forgotten to modify help in Makefile to match the latest changes.
Updated nexush and nexus-cli code to exit with an information msg when there was no embedded certificate and when NEXUS_CERT wasn't defined.

Reworked nexus client build system so that it doesn't depend on any server files, only the public CA certificate
Updated installation doc accordingly

udpated root Makefile

updated docs/install.md

- VM routes and template routes now behave similarily without any exception