Doc update with new USB device

See merge request flg_projects/nexus_vdi/nexus!4

Doh! vmattach was blocking instead of being asynchronous (probably a change used for debugging that I forgot to revert).
Bumpped to version 1.11.2

client: usersetcaps, vmaddaccess now display capabilities in alphabetical order; fixed missing carriage return in usersetcaps
Bumpped client to version 1.11.1

Reworked nexus-exam a bit to be more robust to errors and added recurrent token refresh to fix issue #145 "nexus-exam to renew its jwt token recurrently"

updated Makefile so that CERT defines the path to the public CA certificate instead of its directory. It makes more sense and is more consistent with the rest of the build process (notably live-exam-iso)

Added numlock to always be on

- power button now works on host OS
- brightness set to 100%
- disabled screen blanking
- updated to latest nexus-exam with authentication