Support of Protected mode

[mastracu]

Associate a password to each known printer to manage it when it is in protected mode.
We could leverage known printers list to add password.

[mastracu]

We need to develop better what we mean by support of protected mode.
Regardless of whether a JSON command is protected or not we can embed it in a protected mode command json command.
If the printer is known to be protected then we can ask the user whether he wants to conver it into protected.
This applies to CONFIG channel console command list.