X2Go server (extension support)

 X2Go is a server based computing environment with
    - session resuming
    - low bandwidth support
    - session brokerage support
    - client side mass storage mounting support
    - audio support
    - authentication by smartcard and USB stick
 .
 The X2Go server extension namespace offers contributors to add script
 functionality to X2Go that is not needed/ignored by the legacy X2Go
 client (x2goclient).