See Zammad#13416
Support for new XenServer Updates system with authentication:
- User downloads Client ID JSON file from XenServer account
- User uploads it to XO in their user preferences
- XO uses `username` and `apikey` from that file to authenticate and download updates
- add missing syntaxes
- don't put prompt if no command outputs to ease copy/paste and use `sh` syntax
- always use `$` as prompt and use `console` syntax
